diff --git a/doc/ft-ruby-syntax.txt b/doc/ft-ruby-syntax.txt
index fdf88a0e..46dc2695 100644
--- a/doc/ft-ruby-syntax.txt
+++ b/doc/ft-ruby-syntax.txt
@@ -5,7 +5,8 @@ There are a number of options to the Ruby syntax highlighting.
 1. Ruby operators                     |ruby_operators|
 2. Whitespace errors                  |ruby_space_errors|
 3. Folds                              |ruby_fold|
-4. Reducing expensive operations      |ruby_no_expensive| |ruby_minlines|
+4. Foldable groups                    |ruby_foldable_groups|
+5. Reducing expensive operations      |ruby_no_expensive| |ruby_minlines|
 
 
 1. Ruby operators				*ruby_operators*
@@ -39,7 +40,40 @@ Folds can be enabled by defining "ruby_fold": >
 This will set the value |foldmethod| to "syntax" locally to the current buffer
 or window, which will enable syntax-based folding when editing Ruby filetypes.
 
-4. Reducing expensive operations		*ruby_no_expensive*
+4. Foldable groups				*ruby_foldable_groups*
+
+Default folding is rather detailed, i.e., small syntax units like "if", "do",
+"%w[]" may create corresponding fold levels.
+
+You can set "ruby_foldable_groups" to restrict which groups are foldable: >
+
+        :let ruby_foldable_groups = 'if case %'
+<
+value is space-separated keywords, known keywords were:
+
+    keyword       meaning ~
+    --------  ------------------------------------- ~
+    ALL        Most block syntax (default)
+    NONE       Nothing
+    if         "if" or "unless" block
+    def        "def" block
+    class      "class" block
+    module     "module" block
+    do         "do" block
+    begin      "begin" block
+    case       "case" block
+    for        "for", "while", "until" loops
+    {          Curly bracket block or hash literal
+    [          Array literal
+    %          Literal with "%" notation, e.g.: %w(STRING), %!STRING!
+    /          Regexp
+    string     String and shell command output (surrounded by ', ", `)
+    :          Symbol
+    #          Multiline comment
+    <<         Here documents
+    __END__    Source code after "__END__" directive
+
+5. Reducing expensive operations		*ruby_no_expensive*
 
 By default, the "end" keyword is colorized according to the opening statement
 of the block it closes.  While useful, this feature can be expensive; if you
diff --git a/etc/examples/generators/syntax.rb b/etc/examples/generators/syntax.rb
new file mode 100755
index 00000000..06cf1600
--- /dev/null
+++ b/etc/examples/generators/syntax.rb
@@ -0,0 +1,621 @@
+#!/usr/bin/env ruby
+
+arg = ARGV.pop
+
+
+# Usage example:
+#
+#   ./etc/examples/generators/syntax.rb %Q > etc/examples/syntax/Q.rb
+#
+# then read the output file with 'foldlevel' 0
+
+puts "# Generated by `" <<
+     "./etc/examples/generators/syntax.rb #{arg}" <<
+     " > etc/examples/syntax/#{arg.sub('%', '')}.rb" <<
+     "`\n\n"
+
+
+
+# %Q {{{
+# Generalized Double Quoted String and Array of Strings and Shell Command Output
+if arg == '%Q'
+  # Note: %= is not matched here as the beginning of a double quoted string
+  %Q[~`!@\#$%^&*_-+|:;"',.?/].split(//).each do |s|
+    puts <<-END.gsub(/^\s{4}/, '')
+      %#{s}
+        foo
+        \\#{s}
+        \\\\\\#{s}
+        bar
+      #{s}
+
+
+    END
+  end
+
+  %w(Q W x).each do |leading|
+    %Q[~`!@\#$%^&*_-+=|:;"',.?/].split(//).each do |s|
+      puts <<-END.gsub(/^\s{6}/, '')
+        %#{leading}#{s}
+          foo
+          \\#{s}
+          \\\\\\#{s}
+          bar
+        #{s}
+
+
+      END
+    end
+
+    %w({} <> [] ()).each do |pair|
+      puts <<-END.gsub(/^\s{6}/, '')
+        %#{leading}#{pair[0]}
+          foo
+          \\#{pair[1]}
+          \\\\\\#{pair[1]}
+          bar
+        #{pair[1]}
+
+
+      END
+    end
+
+    puts "  %#{leading} foo\\ \\\\\\ bar\nbaz \n\n" unless leading == 'W'
+  end
+end
+# }}}
+
+
+
+# %q {{{
+# Generalized Single Quoted String, Symbol and Array of Strings
+if arg == '%q'
+  %w(q w s).each do |leading|
+    %Q[~`!@\#$%^&*_-+=|:;"',.?/].split(//).each do |s|
+      puts <<-END.gsub(/^\s{6}/, '')
+        %#{leading}#{s}
+          foo
+          \\#{s}
+          \\\\\\#{s}
+          bar
+        #{s}
+
+
+      END
+    end
+
+    %w({} <> [] ()).each do |pair|
+      puts <<-END.gsub(/^\s{6}/, '')
+        %#{leading}#{pair[0]}
+          foo
+          \\#{pair[1]}
+          \\\\\\#{pair[1]}
+          bar
+        #{pair[1]}
+
+
+      END
+    end
+
+    puts "  %#{leading} foo\\ \\\\\\ bar\nbaz \n\n" unless leading == 'w'
+  end
+end
+# }}}
+
+
+
+# %r {{{
+# Generalized Regular Expression
+if arg == '%r'
+  %Q[~`!@\#$%^&*_-+=|:;"',.?/].split(//).each do |s|
+    puts <<-END.gsub(/^\s{4}/, '')
+      %r#{s}
+        foo
+        \\#{s}
+        \\\\\\#{s}
+        bar
+      #{s}
+
+
+    END
+  end
+
+  puts "  %r foo\\ \\\\\\ bar\nbaz \n\n"
+
+  %w({} <> [] ()).each do |pair|
+    puts <<-END.gsub(/^\s{4}/, '')
+      %r#{pair[0]}
+        foo
+        \\#{pair[1]}
+        \\\\\\#{pair[1]}
+        bar
+      #{pair[1]}
+
+
+    END
+  end
+end
+# }}}
+
+
+
+# %i / %I {{{
+# Array of Symbols
+# Array of interpolated Symbols
+if %w(%i %I).include?(arg)
+  %w(i I).each do |leading|
+    %Q[~`!@\#$%^&*_-+=|:;"',.?/].split(//).each do |s|
+      puts <<-END.gsub(/^\s{6}/, '')
+        %#{leading}#{s}
+          foo
+          \\#{s}
+          \\\\\\#{s}
+          bar
+        #{s}
+
+
+      END
+    end
+
+    %w({} <> [] ()).each do |pair|
+      puts <<-END.gsub(/^\s{6}/, '')
+        %#{leading}#{pair[0]}
+          foo
+          \\#{pair[1]}
+          \\\\\\#{pair[1]}
+          bar
+        #{pair[1]}
+
+
+      END
+    end
+  end
+end
+# }}}
+
+
+
+# string  {{{
+# Normal String and Shell Command Output
+if arg == 'string'
+  %w(' " `).each do |quote|
+    puts <<-END.gsub(/^\s{4}/, '')
+      #{quote}
+        foo
+        \\#{quote}
+        \\\\\\#{quote}
+        bar
+      #{quote}
+
+
+    END
+  end
+end
+# }}}
+
+
+
+# regex (Normal Regular Expression) {{{
+if arg == 'regexp'
+  'iomxneus'.split('').unshift('').each do |option|
+    puts "\n# Begin test for option '#{option}' {{{\n\n"
+
+    puts <<-END.gsub(/^\s{4}/, '')
+        /
+          foo
+          \\\/
+          \\\\\\\/
+          bar
+        /#{option}
+
+
+    END
+
+    %w(and or while until unless if elsif when not then else).each do |s|
+      puts <<-END.gsub(/^\s{6}/, '')
+        #{s}/
+          foo
+          \\\/
+          \\\\\\\/
+          bar
+        /#{option}
+
+
+      END
+    end
+
+    %w(; \ ~ = ! | \( & , { [ < > ? : * + -).each do |s|
+      puts <<-END.gsub(/^\s{6}/, '')
+        #{s}/
+          foo
+          \\\/
+          \\\\\\\/
+          bar
+        /#{option}
+
+
+      END
+    end
+
+    [' ', "\t", '=', 'OK'].each do |s|
+      puts <<-END.gsub(/^\s{6}/, '')
+        _foo  /#{s}
+          foo
+          \\\/
+          \\\\\\\/
+          bar
+        /#{option}
+
+
+      END
+    end
+
+    puts "# }}} End test for option '#{option}'\n"
+  end
+
+  puts "\n# Test for ternary operation (8c1c484) {{{\n\n"
+  puts 'yo = 4 ? /quack#{3}/ : /quack/'
+  puts "\n# }}} End test for ternary operation\n"
+end
+# }}}
+
+
+
+# symbol {{{
+# Symbol region
+if arg == 'symbol'
+  %w(' ").each do |quote|
+    %Q_]})\"':_.split(//).unshift('').each do |s|
+      puts <<-END.gsub(/^\s{6}/, '')
+        #{s}:#{quote}
+          foo
+          \\#{quote}
+          \\\\\\#{quote}
+          bar
+        #{quote}
+      #{"  #{s} # close string to ensure next case clean" if %w(' ").include?(s) && s != quote }
+
+
+      END
+    end
+  end
+end
+# }}}
+
+
+
+# heredoc {{{
+# Here Documents
+if arg == 'heredoc'
+  puts "\n# Begin of valid cases {{{\n\n"
+
+  %w(' " `).unshift('').each do |quote|
+    puts <<-END.gsub(/^\s{6}/, '')
+        <<#{quote}_LABEL#{quote}.?!, foo
+          bar baz
+      _LABEL
+      \n
+
+        <<-#{quote}_LABEL#{quote}.?!, foo
+          bar baz
+        _LABEL
+      \n
+
+          <<~#{quote}_LABEL#{quote}.?!, foo
+            bar baz
+          _LABEL
+
+
+    END
+  end
+
+  puts "# }}} End of valid cases'\n\n"
+
+
+  puts "\n# Begin of INVALID cases {{{\n\n"
+
+  # NOTE: for simplification, omit test for different quotes " ' `,
+  # they are all invalid anyway
+
+  %w(class ::).each do |s|
+    puts <<-END.gsub(/^\s{6}/, '')
+      #{s}\n <<LABEL
+        foo
+      LABEL
+
+
+    END
+  end
+
+  %Q_]})\"'._.split(//).each do |s|
+    puts <<-END.gsub(/^\s{4}/, '')
+    #{s} <<LABEL
+      foo
+    LABEL
+    #{"  #{s} # close to ensure next case clean" if %w(' ").include?(s)}
+
+    END
+  end
+
+  %w(09 aZ _w).each do |s|
+    puts <<-END.gsub(/^\s{6}/, '')
+      #{s}<<LABEL
+        foo
+      LABEL
+
+
+    END
+  end
+
+  %w(' " `).unshift('').each do |quote|
+    puts <<-END.gsub(/^\s{6}/, '')
+      <<LABEL foo<<#{quote}_bar
+        baz
+      LABEL
+      #{"  #{quote} # close to ensure next case clean" if %w(' ").include?(quote)}
+      \n
+
+      <<LABEL foo<<-#{quote}_bar
+        baz
+      LABEL
+      #{"  #{quote} # close to ensure next case clean" if %w(' ").include?(quote)}
+
+
+    END
+  end
+
+  puts "# }}} End of INVALID cases'\n\n"
+end
+# }}}
+
+
+
+# blocks  {{{
+# simple blocks (def, class, module, do, begin, case)
+if arg == 'blocks'
+  puts <<-END.gsub(/^\s{4}/, '')
+    def
+      foo
+      def
+        bar
+      end
+    end
+
+
+  END
+
+  %w(class module do begin case).each do |s|
+    puts <<-END.gsub(/^\s{6}/, '')
+      #{s}
+        foo
+      end
+
+
+    END
+  end
+end
+# }}}
+
+
+
+# brackets  {{{
+# curly bracket block and hash literal
+if arg == 'brackets'
+  puts <<-END.gsub(/^\s{4}/, '')
+    {
+      foo
+    }
+
+
+  END
+
+  %w<_xxx ] } )>.unshift('').each do |s|
+    puts <<-END.gsub(/^\s{6}/, '')
+      #{s}[
+        foo
+      ]
+
+
+    END
+  end
+end
+# }}}
+
+
+
+# if {{{
+# if/else blocks
+if arg == 'if'
+  %w(if unless).each do |start|
+    puts <<-END.gsub(/^ {6}/, '')
+      #{start} 1
+        foo
+      else
+        bar
+      end
+
+      foo \\
+        #{start} 1
+          foo
+        else
+          bar
+        end
+
+      baz ...= #{start} 1
+        foo
+      else
+        bar
+      end
+
+
+    END
+
+    ['?', '!'].each do |mark|
+      puts <<-END.gsub(/^ {8}/, '')
+        42foo#{mark} #{start} 1
+          bar
+        else
+          baz
+        end
+
+
+      END
+    end
+
+    '{:,;([<>~\*%&^|+=-'.split(//).each do |expr|
+      puts <<-END.gsub(/^ {8}/, '')
+        foo #{expr} #{start} 1
+          bar
+        else
+          baz
+        end
+
+
+      END
+    end
+
+    # c7cb532 match correct `end`
+    puts <<-END.gsub(/^ {6}/, '')
+      #{start} 1
+        (1..5).end
+        :: end
+      end
+
+      #{start} 1
+      ..end
+
+
+    END
+
+    # INVALID cases
+    puts <<-END.gsub(/^ {6}/, '')
+      not_BOF #{start} 1
+        bar
+      else
+        baz
+      end
+
+
+    END
+
+    ['?', '!'].each do |mark|
+      puts <<-END.gsub(/^ {8}/, '')
+        _foo#{mark} #{start} 1
+          bar
+        else
+          baz
+        end
+
+
+      END
+    end
+  end
+end
+# }}}
+
+
+
+# for {{{
+# rubyRepeatExpression (for, while, until)
+if arg == 'for'
+  puts <<-END.gsub(/^ {4}/, '')
+    for 1
+      foo
+    end
+
+
+  END
+
+  %w(until while).each do |start|
+    puts <<-END.gsub(/^ {6}/, '')
+      #{start} 1
+        foo
+      end
+
+
+      baz ...= #{start} 1
+        foo
+      end
+
+
+    END
+
+    '{:,;([<>~\*/%&^|+-'.split(//).each do |expr|
+      puts <<-END.gsub(/^ {8}/, '')
+        foo #{expr} #{start} 1
+          bar
+        end
+
+
+      END
+    end
+
+    # INVALID cases
+    puts <<-END.gsub(/^ {6}/, '')
+      not_BOF #{start} 1
+        bar
+      end
+
+
+    END
+
+    ['?', '!'].each do |mark|
+      puts <<-END.gsub(/^ {8}/, '')
+        _foo#{mark} #{start} 1
+          bar
+        end
+
+
+      END
+    end
+  end
+end
+# }}}
+
+
+
+# comment {{{
+if arg == 'comment'
+  puts <<-END.gsub(/^ {4}/, '')
+      # foo
+      # foo
+        # bar
+
+      baz
+
+
+
+    =begin foo bar
+      comment
+    =end baz
+
+
+  END
+end
+# }}}
+
+
+
+# __END__ {{{
+if arg == '__END__'
+  puts <<-EOF.gsub(/^ {4}/, '')
+      __END__
+      invalid
+      invalid
+
+
+    __END__
+      valid
+      valid
+
+
+  EOF
+end
+# }}}
+
+
+
+puts "#\svim:foldmethod=syntax"
+
+
+# vim:foldmethod=marker
diff --git a/syntax/ruby.vim b/syntax/ruby.vim
index 9c155c71..342383eb 100644
--- a/syntax/ruby.vim
+++ b/syntax/ruby.vim
@@ -17,6 +17,29 @@ if has("folding") && exists("ruby_fold")
   setlocal foldmethod=syntax
 endif
 
+let s:foldable_groups = split(
+      \	  get(
+      \	    b:,
+      \	    'ruby_foldable_groups',
+      \	    get(g:, 'ruby_foldable_groups', 'ALL')
+      \	  )
+      \	)
+
+function! s:foldable(...) abort "{{{
+  if index(s:foldable_groups, 'ALL') > -1
+    return 1
+  endif
+
+  for l:i in a:000
+    if index(s:foldable_groups, l:i) > -1
+      return 1
+    endif
+  endfor
+
+  return 0
+endfunction "}}}
+
+
 syn cluster rubyNotTop contains=@rubyExtendedStringSpecial,@rubyRegexpSpecial,@rubyDeclaration,rubyConditional,rubyExceptional,rubyMethodExceptional,rubyTodo
 
 if exists("ruby_space_errors")
@@ -100,8 +123,14 @@ syn match  rubySymbol		"[]})\"':]\@<!:\%(\^\|\~@\|\~\|<<\|<=>\|<=\|<\|===\|[=!]=
 syn match  rubySymbol		"[]})\"':]\@<!:\$\%(-.\|[`~<=>_,;:!?/.'"@$*\&+0]\)"
 syn match  rubySymbol		"[]})\"':]\@<!:\%(\$\|@@\=\)\=\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*"
 syn match  rubySymbol		"[]})\"':]\@<!:\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*\%([?!=]>\@!\)\="
-syn region rubySymbol		start="[]})\"':]\@<!:'"  end="'"  skip="\\\\\|\\'"  contains=rubyQuoteEscape fold
-syn region rubySymbol		start="[]})\"':]\@<!:\"" end="\"" skip="\\\\\|\\\"" contains=@rubyStringSpecial fold
+
+if s:foldable(':')
+  syn region rubySymbol		start="[]})\"':]\@<!:'"  end="'"  skip="\\\\\|\\'"  contains=rubyQuoteEscape fold
+  syn region rubySymbol		start="[]})\"':]\@<!:\"" end="\"" skip="\\\\\|\\\"" contains=@rubyStringSpecial fold
+else
+  syn region rubySymbol		start="[]})\"':]\@<!:'"  end="'"  skip="\\\\\|\\'"  contains=rubyQuoteEscape
+  syn region rubySymbol		start="[]})\"':]\@<!:\"" end="\"" skip="\\\\\|\\\"" contains=@rubyStringSpecial
+endif
 
 syn match  rubyCapitalizedMethod	"\%(\%(^\|[^.]\)\.\s*\)\@<!\<\u\%(\w\|[^\x00-\x7F]\)*\>\%(\s*(\)*\s*(\@="
 
@@ -119,62 +148,123 @@ syn match rubyPredefinedConstant "\%(\%(^\|[^.]\)\.\s*\)\@<!\<\%(ARGF\|ARGV\|ENV
 syn match rubyPredefinedConstant "\%(\%(^\|[^.]\)\.\s*\)\@<!\<\%(RUBY_\%(VERSION\|RELEASE_DATE\|PLATFORM\|PATCHLEVEL\|REVISION\|DESCRIPTION\|COPYRIGHT\|ENGINE\)\)\>\%(\s*(\)\@!"
 
 " Normal Regular Expression
-syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="\%(\%(^\|\<\%(and\|or\|while\|until\|unless\|if\|elsif\|when\|not\|then\|else\)\|[;\~=!|&(,{[<>?:*+-]\)\s*\)\@<=/" end="/[iomxneus]*" skip="\\\\\|\\/" contains=@rubyRegexpSpecial fold
-syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="\%(\h\k*\s\+\)\@<=/[ \t=]\@!" end="/[iomxneus]*" skip="\\\\\|\\/" contains=@rubyRegexpSpecial fold
+if s:foldable('/')
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="\%(\%(^\|\<\%(and\|or\|while\|until\|unless\|if\|elsif\|when\|not\|then\|else\)\|[;\~=!|&(,{[<>?:*+-]\)\s*\)\@<=/" end="/[iomxneus]*" skip="\\\\\|\\/" contains=@rubyRegexpSpecial fold
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="\%(\h\k*\s\+\)\@<=/[ \t=]\@!" end="/[iomxneus]*" skip="\\\\\|\\/" contains=@rubyRegexpSpecial fold
+else
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="\%(\%(^\|\<\%(and\|or\|while\|until\|unless\|if\|elsif\|when\|not\|then\|else\)\|[;\~=!|&(,{[<>?:*+-]\)\s*\)\@<=/" end="/[iomxneus]*" skip="\\\\\|\\/" contains=@rubyRegexpSpecial
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="\%(\h\k*\s\+\)\@<=/[ \t=]\@!" end="/[iomxneus]*" skip="\\\\\|\\/" contains=@rubyRegexpSpecial
+endif
 
 " Generalized Regular Expression
-syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1[iomxneus]*" skip="\\\\\|\\\z1" contains=@rubyRegexpSpecial fold
-syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r{"				end="}[iomxneus]*"   skip="\\\\\|\\}"	 contains=@rubyRegexpSpecial fold
-syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r<"				end=">[iomxneus]*"   skip="\\\\\|\\>"	 contains=@rubyRegexpSpecial,rubyNestedAngleBrackets,rubyDelimEscape fold
-syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\["				end="\][iomxneus]*"  skip="\\\\\|\\\]"	 contains=@rubyRegexpSpecial fold
-syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r("				end=")[iomxneus]*"   skip="\\\\\|\\)"	 contains=@rubyRegexpSpecial fold
-syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\z(\s\)"				end="\z1[iomxneus]*" skip="\\\\\|\\\z1" contains=@rubyRegexpSpecial fold
-
-" Normal String
+if s:foldable('%')
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1[iomxneus]*" skip="\\\\\|\\\z1" contains=@rubyRegexpSpecial fold
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r{"				end="}[iomxneus]*"   skip="\\\\\|\\}"	 contains=@rubyRegexpSpecial fold
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r<"				end=">[iomxneus]*"   skip="\\\\\|\\>"	 contains=@rubyRegexpSpecial,rubyNestedAngleBrackets,rubyDelimEscape fold
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\["				end="\][iomxneus]*"  skip="\\\\\|\\\]"	 contains=@rubyRegexpSpecial fold
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r("				end=")[iomxneus]*"   skip="\\\\\|\\)"	 contains=@rubyRegexpSpecial fold
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\z(\s\)"				end="\z1[iomxneus]*" skip="\\\\\|\\\z1" contains=@rubyRegexpSpecial fold
+else
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1[iomxneus]*" skip="\\\\\|\\\z1" contains=@rubyRegexpSpecial
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r{"				end="}[iomxneus]*"   skip="\\\\\|\\}"	 contains=@rubyRegexpSpecial
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r<"				end=">[iomxneus]*"   skip="\\\\\|\\>"	 contains=@rubyRegexpSpecial,rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\["				end="\][iomxneus]*"  skip="\\\\\|\\\]"	 contains=@rubyRegexpSpecial
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r("				end=")[iomxneus]*"   skip="\\\\\|\\)"	 contains=@rubyRegexpSpecial
+  syn region rubyRegexp matchgroup=rubyRegexpDelimiter start="%r\z(\s\)"				end="\z1[iomxneus]*" skip="\\\\\|\\\z1" contains=@rubyRegexpSpecial
+endif
+
+" Normal String and Shell Command Output
 let s:spell_cluster = exists('ruby_spellcheck_strings') ? ',@Spell' : ''
-exe 'syn region rubyString matchgroup=rubyStringDelimiter start="\"" end="\"" skip="\\\\\|\\\"" fold contains=@rubyStringSpecial' . s:spell_cluster
-exe 'syn region rubyString matchgroup=rubyStringDelimiter start="''" end="''" skip="\\\\\|\\''" fold contains=rubyQuoteEscape'    . s:spell_cluster
+exe 'syn region rubyString matchgroup=rubyStringDelimiter start="\"" end="\"" skip="\\\\\|\\\"" ' .
+      \ (s:foldable('%') ? 'fold' : '') . ' contains=@rubyStringSpecial' . s:spell_cluster
+exe 'syn region rubyString matchgroup=rubyStringDelimiter start="''" end="''" skip="\\\\\|\\''" ' .
+      \ (s:foldable('%') ? 'fold' : '') . ' contains=rubyQuoteEscape'    . s:spell_cluster
 
 " Shell Command Output
-syn region rubyString matchgroup=rubyStringDelimiter start="`" end="`" skip="\\\\\|\\`" contains=@rubyStringSpecial fold
+if s:foldable('%')
+  syn region rubyString matchgroup=rubyStringDelimiter start="`" end="`" skip="\\\\\|\\`" contains=@rubyStringSpecial fold
+else
+  syn region rubyString matchgroup=rubyStringDelimiter start="`" end="`" skip="\\\\\|\\`" contains=@rubyStringSpecial
+endif
 
 " Generalized Single Quoted String, Symbol and Array of Strings
-syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1" fold
-syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]{"				   end="}"   skip="\\\\\|\\}"	fold contains=rubyNestedCurlyBraces,rubyDelimEscape
-syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]<"				   end=">"   skip="\\\\\|\\>"	fold contains=rubyNestedAngleBrackets,rubyDelimEscape
-syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]\["				   end="\]"  skip="\\\\\|\\\]"	fold contains=rubyNestedSquareBrackets,rubyDelimEscape
-syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]("				   end=")"   skip="\\\\\|\\)"	fold contains=rubyNestedParentheses,rubyDelimEscape
-syn region rubyString matchgroup=rubyStringDelimiter start="%q\z(\s\)"				   end="\z1" skip="\\\\\|\\\z1" fold
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)"    end="\z1" skip="\\\\\|\\\z1" fold
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s{"				   end="}"   skip="\\\\\|\\}"	fold contains=rubyNestedCurlyBraces,rubyDelimEscape
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s<"				   end=">"   skip="\\\\\|\\>"	fold contains=rubyNestedAngleBrackets,rubyDelimEscape
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s\["				   end="\]"  skip="\\\\\|\\\]"	fold contains=rubyNestedSquareBrackets,rubyDelimEscape
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s("				   end=")"   skip="\\\\\|\\)"	fold contains=rubyNestedParentheses,rubyDelimEscape
-syn region rubyString matchgroup=rubyStringDelimiter start="%s\z(\s\)"				   end="\z1" skip="\\\\\|\\\z1" fold
+if s:foldable('%')
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1" fold
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]{"				     end="}"   skip="\\\\\|\\}"	  fold contains=rubyNestedCurlyBraces,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]<"				     end=">"   skip="\\\\\|\\>"	  fold contains=rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]\["				     end="\]"  skip="\\\\\|\\\]"  fold contains=rubyNestedSquareBrackets,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]("				     end=")"   skip="\\\\\|\\)"	  fold contains=rubyNestedParentheses,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%q\z(\s\)"			     end="\z1" skip="\\\\\|\\\z1" fold
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)"    end="\z1" skip="\\\\\|\\\z1" fold
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s{"				     end="}"   skip="\\\\\|\\}"	  fold contains=rubyNestedCurlyBraces,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s<"				     end=">"   skip="\\\\\|\\>"	  fold contains=rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s\["				     end="\]"  skip="\\\\\|\\\]"  fold contains=rubyNestedSquareBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s("				     end=")"   skip="\\\\\|\\)"	  fold contains=rubyNestedParentheses,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%s\z(\s\)"			     end="\z1" skip="\\\\\|\\\z1" fold
+else
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1"
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]{"				     end="}"   skip="\\\\\|\\}"	  contains=rubyNestedCurlyBraces,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]<"				     end=">"   skip="\\\\\|\\>"	  contains=rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]\["				     end="\]"  skip="\\\\\|\\\]"  contains=rubyNestedSquareBrackets,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[qw]("				     end=")"   skip="\\\\\|\\)"	  contains=rubyNestedParentheses,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%q\z(\s\)"			     end="\z1" skip="\\\\\|\\\z1"
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)"    end="\z1" skip="\\\\\|\\\z1"
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s{"				     end="}"   skip="\\\\\|\\}"	  contains=rubyNestedCurlyBraces,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s<"				     end=">"   skip="\\\\\|\\>"	  contains=rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s\["				     end="\]"  skip="\\\\\|\\\]"  contains=rubyNestedSquareBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%s("				     end=")"   skip="\\\\\|\\)"	  contains=rubyNestedParentheses,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%s\z(\s\)"			     end="\z1" skip="\\\\\|\\\z1"
+endif
 
 " Generalized Double Quoted String and Array of Strings and Shell Command Output
 " Note: %= is not matched here as the beginning of a double quoted string
-syn region rubyString matchgroup=rubyStringDelimiter start="%\z([~`!@#$%^&*_\-+|\:;"',.?/]\)"	    end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial fold
-syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial fold
-syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\={"				    end="}"   skip="\\\\\|\\}"	 contains=@rubyStringSpecial,rubyNestedCurlyBraces,rubyDelimEscape    fold
-syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=<"				    end=">"   skip="\\\\\|\\>"	 contains=@rubyStringSpecial,rubyNestedAngleBrackets,rubyDelimEscape  fold
-syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=\["				    end="\]"  skip="\\\\\|\\\]"	 contains=@rubyStringSpecial,rubyNestedSquareBrackets,rubyDelimEscape fold
-syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=("				    end=")"   skip="\\\\\|\\)"	 contains=@rubyStringSpecial,rubyNestedParentheses,rubyDelimEscape    fold
-syn region rubyString matchgroup=rubyStringDelimiter start="%[Qx]\z(\s\)"			    end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial fold
-
-" Array of Symbols
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1" fold
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i{"				end="}"   skip="\\\\\|\\}"	fold contains=rubyNestedCurlyBraces,rubyDelimEscape
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i<"				end=">"   skip="\\\\\|\\>"	fold contains=rubyNestedAngleBrackets,rubyDelimEscape
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i\["				end="\]"  skip="\\\\\|\\\]"	fold contains=rubyNestedSquareBrackets,rubyDelimEscape
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i("				end=")"   skip="\\\\\|\\)"	fold contains=rubyNestedParentheses,rubyDelimEscape
-
-" Array of interpolated Symbols
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial fold
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I{"				end="}"   skip="\\\\\|\\}"	 contains=@rubyStringSpecial,rubyNestedCurlyBraces,rubyDelimEscape    fold
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I<"				end=">"   skip="\\\\\|\\>"	 contains=@rubyStringSpecial,rubyNestedAngleBrackets,rubyDelimEscape  fold
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I\["				end="\]"  skip="\\\\\|\\\]"	 contains=@rubyStringSpecial,rubyNestedSquareBrackets,rubyDelimEscape fold
-syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I("				end=")"   skip="\\\\\|\\)"	 contains=@rubyStringSpecial,rubyNestedParentheses,rubyDelimEscape    fold
+if s:foldable('%')
+  syn region rubyString matchgroup=rubyStringDelimiter start="%\z([~`!@#$%^&*_\-+|\:;"',.?/]\)"	      end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial fold
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial fold
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\={"			      end="}"   skip="\\\\\|\\}"   contains=@rubyStringSpecial,rubyNestedCurlyBraces,rubyDelimEscape    fold
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=<"			      end=">"   skip="\\\\\|\\>"   contains=@rubyStringSpecial,rubyNestedAngleBrackets,rubyDelimEscape  fold
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=\["			      end="\]"  skip="\\\\\|\\\]"  contains=@rubyStringSpecial,rubyNestedSquareBrackets,rubyDelimEscape fold
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=("			      end=")"   skip="\\\\\|\\)"   contains=@rubyStringSpecial,rubyNestedParentheses,rubyDelimEscape    fold
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[Qx]\z(\s\)"			      end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial fold
+else
+  syn region rubyString matchgroup=rubyStringDelimiter start="%\z([~`!@#$%^&*_\-+|\:;"',.?/]\)"	      end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\={"			      end="}"   skip="\\\\\|\\}"   contains=@rubyStringSpecial,rubyNestedCurlyBraces,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=<"			      end=">"   skip="\\\\\|\\>"   contains=@rubyStringSpecial,rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=\["			      end="\]"  skip="\\\\\|\\\]"  contains=@rubyStringSpecial,rubyNestedSquareBrackets,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[QWx]\=("			      end=")"   skip="\\\\\|\\)"   contains=@rubyStringSpecial,rubyNestedParentheses,rubyDelimEscape
+  syn region rubyString matchgroup=rubyStringDelimiter start="%[Qx]\z(\s\)"			      end="\z1" skip="\\\\\|\\\z1" contains=@rubyStringSpecial
+endif
+
+if s:foldable('%')
+  " Array of Symbols
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1"	fold
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i{"				  end="}"   skip="\\\\\|\\}"	fold contains=rubyNestedCurlyBraces,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i<"				  end=">"   skip="\\\\\|\\>"	fold contains=rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i\["				  end="\]"  skip="\\\\\|\\\]"	fold contains=rubyNestedSquareBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i("				  end=")"   skip="\\\\\|\\)"	fold contains=rubyNestedParentheses,rubyDelimEscape
+
+  " Array of interpolated Symbols
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1"	contains=@rubyStringSpecial fold
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I{"				  end="}"   skip="\\\\\|\\}"	contains=@rubyStringSpecial,rubyNestedCurlyBraces,rubyDelimEscape    fold
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I<"				  end=">"   skip="\\\\\|\\>"	contains=@rubyStringSpecial,rubyNestedAngleBrackets,rubyDelimEscape  fold
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I\["				  end="\]"  skip="\\\\\|\\\]"	contains=@rubyStringSpecial,rubyNestedSquareBrackets,rubyDelimEscape fold
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I("				  end=")"   skip="\\\\\|\\)"	contains=@rubyStringSpecial,rubyNestedParentheses,rubyDelimEscape    fold
+else
+  " Array of Symbols
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1"
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i{"				  end="}"   skip="\\\\\|\\}"	contains=rubyNestedCurlyBraces,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i<"				  end=">"   skip="\\\\\|\\>"	contains=rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i\["				  end="\]"  skip="\\\\\|\\\]"	contains=rubyNestedSquareBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%i("				  end=")"   skip="\\\\\|\\)"	contains=rubyNestedParentheses,rubyDelimEscape
+
+  " Array of interpolated Symbols
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I\z([~`!@#$%^&*_\-+=|\:;"',.?/]\)" end="\z1" skip="\\\\\|\\\z1"	contains=@rubyStringSpecial
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I{"				  end="}"   skip="\\\\\|\\}"	contains=@rubyStringSpecial,rubyNestedCurlyBraces,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I<"				  end=">"   skip="\\\\\|\\>"	contains=@rubyStringSpecial,rubyNestedAngleBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I\["				  end="\]"  skip="\\\\\|\\\]"	contains=@rubyStringSpecial,rubyNestedSquareBrackets,rubyDelimEscape
+  syn region rubySymbol matchgroup=rubySymbolDelimiter start="%I("				  end=")"   skip="\\\\\|\\)"	contains=@rubyStringSpecial,rubyNestedParentheses,rubyDelimEscape
+endif
 
 " Here Document
 syn region rubyHeredocStart matchgroup=rubyStringDelimiter start=+\%(\%(class\s*\|\%([]})"'.]\|::\)\)\_s*\|\w\)\@<!<<[-~]\=\zs\%(\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*\)+	 end=+$+ oneline contains=ALLBUT,@rubyNotTop
@@ -182,15 +272,27 @@ syn region rubyHeredocStart matchgroup=rubyStringDelimiter start=+\%(\%(class\s*
 syn region rubyHeredocStart matchgroup=rubyStringDelimiter start=+\%(\%(class\s*\|\%([]})"'.]\|::\)\)\_s*\|\w\)\@<!<<[-~]\=\zs'\%([^']*\)'+ end=+$+ oneline contains=ALLBUT,@rubyNotTop
 syn region rubyHeredocStart matchgroup=rubyStringDelimiter start=+\%(\%(class\s*\|\%([]})"'.]\|::\)\)\_s*\|\w\)\@<!<<[-~]\=\zs`\%([^`]*\)`+ end=+$+ oneline contains=ALLBUT,@rubyNotTop
 
-syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<\z(\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*\)\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial fold keepend
-syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<"\z([^"]*\)"\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial fold keepend
-syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<'\z([^']*\)'\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc			fold keepend
-syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<`\z([^`]*\)`\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial fold keepend
+if s:foldable('<<')
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<\z(\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*\)\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial fold keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<"\z([^"]*\)"\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial fold keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<'\z([^']*\)'\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc		    fold keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<`\z([^`]*\)`\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial fold keepend
 
-syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]\z(\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*\)\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3    matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial fold keepend
-syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]"\z([^"]*\)"\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial fold keepend
-syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]'\z([^']*\)'\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart		     fold keepend
-syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]`\z([^`]*\)`\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial fold keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]\z(\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*\)\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3    matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial fold keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]"\z([^"]*\)"\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial fold keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]'\z([^']*\)'\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart		    fold keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]`\z([^`]*\)`\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial fold keepend
+else
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<\z(\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*\)\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<"\z([^"]*\)"\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<'\z([^']*\)'\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc		    keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]})"'.]\)\s\|\w\)\@<!<<`\z([^`]*\)`\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+2	matchgroup=rubyStringDelimiter end=+^\z1$+ contains=rubyHeredocStart,rubyHeredoc,@rubyStringSpecial keepend
+
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]\z(\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*\)\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3    matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]"\z([^"]*\)"\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]'\z([^']*\)'\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart		    keepend
+  syn region rubyString start=+\%(\%(class\|::\)\_s*\|\%([]}).]\)\s\|\w\)\@<!<<[-~]`\z([^`]*\)`\ze\%(.*<<[-~]\=['`"]\=\h\)\@!+hs=s+3  matchgroup=rubyStringDelimiter end=+^\s*\zs\z1$+ contains=rubyHeredocStart,@rubyStringSpecial keepend
+endif
 
 if exists('main_syntax') && main_syntax == 'eruby'
   let b:ruby_no_expensive = 1
@@ -226,23 +328,65 @@ if !exists("b:ruby_no_expensive") && !exists("ruby_no_expensive")
   syn match  rubyClass	"\<class\>"  nextgroup=rubyClassDeclaration  skipwhite skipnl
   syn match  rubyModule "\<module\>" nextgroup=rubyModuleDeclaration skipwhite skipnl
 
-  syn region rubyMethodBlock start="\<def\>"	matchgroup=rubyDefine end="\%(\<def\_s\+\)\@<!\<end\>" contains=ALLBUT,@rubyNotTop fold
-  syn region rubyBlock	     start="\<class\>"	matchgroup=rubyClass  end="\<end\>"		       contains=ALLBUT,@rubyNotTop fold
-  syn region rubyBlock	     start="\<module\>" matchgroup=rubyModule end="\<end\>"		       contains=ALLBUT,@rubyNotTop fold
+  if s:foldable('def')
+    syn region rubyMethodBlock start="\<def\>"	matchgroup=rubyDefine end="\%(\<def\_s\+\)\@<!\<end\>" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyMethodBlock start="\<def\>"	matchgroup=rubyDefine end="\%(\<def\_s\+\)\@<!\<end\>" contains=ALLBUT,@rubyNotTop
+  endif
+
+  if s:foldable('class')
+    syn region rubyBlock start="\<class\>"	matchgroup=rubyClass end="\<end\>" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyBlock start="\<class\>"	matchgroup=rubyClass end="\<end\>" contains=ALLBUT,@rubyNotTop
+  endif
+
+  if s:foldable('module')
+    syn region rubyBlock start="\<module\>" matchgroup=rubyModule end="\<end\>" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyBlock start="\<module\>" matchgroup=rubyModule end="\<end\>" contains=ALLBUT,@rubyNotTop
+  endif
 
   " modifiers
   syn match rubyConditionalModifier "\<\%(if\|unless\)\>"    display
   syn match rubyRepeatModifier	     "\<\%(while\|until\)\>" display
 
-  syn region rubyDoBlock      matchgroup=rubyControl start="\<do\>" end="\<end\>"                 contains=ALLBUT,@rubyNotTop fold
+  if s:foldable('do')
+    syn region rubyDoBlock matchgroup=rubyControl start="\<do\>" end="\<end\>" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyDoBlock matchgroup=rubyControl start="\<do\>" end="\<end\>" contains=ALLBUT,@rubyNotTop
+  endif
+
   " curly bracket block or hash literal
-  syn region rubyCurlyBlock	matchgroup=rubyCurlyBlockDelimiter  start="{" end="}"				contains=ALLBUT,@rubyNotTop fold
-  syn region rubyArrayLiteral	matchgroup=rubyArrayDelimiter	    start="\%(\w\|[\]})]\)\@<!\[" end="]"	contains=ALLBUT,@rubyNotTop fold
+  if s:foldable('{')
+    syn region rubyCurlyBlock matchgroup=rubyCurlyBlockDelimiter start="{" end="}" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyCurlyBlock matchgroup=rubyCurlyBlockDelimiter start="{" end="}" contains=ALLBUT,@rubyNotTop
+  endif
+
+  if s:foldable('[')
+    syn region rubyArrayLiteral	matchgroup=rubyArrayDelimiter start="\%(\w\|[\]})]\)\@<!\[" end="]" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyArrayLiteral	matchgroup=rubyArrayDelimiter start="\%(\w\|[\]})]\)\@<!\[" end="]" contains=ALLBUT,@rubyNotTop
+  endif
 
   " statements without 'do'
-  syn region rubyBlockExpression       matchgroup=rubyControl	  start="\<begin\>" end="\<end\>" contains=ALLBUT,@rubyNotTop fold
-  syn region rubyCaseExpression	       matchgroup=rubyConditional start="\<case\>"  end="\<end\>" contains=ALLBUT,@rubyNotTop fold
-  syn region rubyConditionalExpression matchgroup=rubyConditional start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*%&^|+=-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![?!]\)\s*\)\@<=\%(\\\n\s*\)\@<!\%(if\|unless\)\>" end="\%(\%(\%(\.\@<!\.\)\|::\)\s*\)\@<!\<end\>" contains=ALLBUT,@rubyNotTop fold
+  if s:foldable('begin')
+    syn region rubyBlockExpression matchgroup=rubyControl start="\<begin\>" end="\<end\>" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyBlockExpression matchgroup=rubyControl start="\<begin\>" end="\<end\>" contains=ALLBUT,@rubyNotTop
+  endif
+
+  if s:foldable('case')
+    syn region rubyCaseExpression matchgroup=rubyConditional start="\<case\>" end="\<end\>" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyCaseExpression matchgroup=rubyConditional start="\<case\>" end="\<end\>" contains=ALLBUT,@rubyNotTop
+  endif
+
+  if s:foldable('if')
+    syn region rubyConditionalExpression matchgroup=rubyConditional start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*%&^|+=-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![?!]\)\s*\)\@<=\%(\\\n\s*\)\@<!\%(if\|unless\)\>" end="\%(\%(\%(\.\@<!\.\)\|::\)\s*\)\@<!\<end\>" contains=ALLBUT,@rubyNotTop fold
+  else
+    syn region rubyConditionalExpression matchgroup=rubyConditional start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*%&^|+=-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![?!]\)\s*\)\@<=\%(\\\n\s*\)\@<!\%(if\|unless\)\>" end="\%(\%(\%(\.\@<!\.\)\|::\)\s*\)\@<!\<end\>" contains=ALLBUT,@rubyNotTop
+  endif
 
   syn match rubyConditional "\<\%(then\|else\|when\)\>[?!]\@!"	contained containedin=rubyCaseExpression
   syn match rubyConditional "\<\%(then\|else\|elsif\)\>[?!]\@!" contained containedin=rubyConditionalExpression
@@ -252,7 +396,12 @@ if !exists("b:ruby_no_expensive") && !exists("ruby_no_expensive")
 
   " statements with optional 'do'
   syn region rubyOptionalDoLine   matchgroup=rubyRepeat start="\<for\>[?!]\@!" start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*/%&^|+-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![!=?]\)\s*\)\@<=\<\%(until\|while\)\>" matchgroup=rubyOptionalDo end="\%(\<do\>\)" end="\ze\%(;\|$\)" oneline contains=ALLBUT,@rubyNotTop
-  syn region rubyRepeatExpression start="\<for\>[?!]\@!" start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*/%&^|+-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![!=?]\)\s*\)\@<=\<\%(until\|while\)\>" matchgroup=rubyRepeat end="\<end\>" contains=ALLBUT,@rubyNotTop nextgroup=rubyOptionalDoLine fold
+
+  if s:foldable('for')
+    syn region rubyRepeatExpression start="\<for\>[?!]\@!" start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*/%&^|+-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![!=?]\)\s*\)\@<=\<\%(until\|while\)\>" matchgroup=rubyRepeat end="\<end\>" contains=ALLBUT,@rubyNotTop nextgroup=rubyOptionalDoLine fold
+  else
+    syn region rubyRepeatExpression start="\<for\>[?!]\@!" start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*/%&^|+-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![!=?]\)\s*\)\@<=\<\%(until\|while\)\>" matchgroup=rubyRepeat end="\<end\>" contains=ALLBUT,@rubyNotTop nextgroup=rubyOptionalDoLine
+  endif
 
   if !exists("ruby_minlines")
     let ruby_minlines = 500
@@ -286,7 +435,7 @@ endif
 syn match   rubySharpBang "\%^#!.*" display
 syn keyword rubyTodo	  FIXME NOTE TODO OPTIMIZE HACK REVIEW XXX todo contained
 syn match   rubyComment   "#.*" contains=rubySharpBang,rubySpaceError,rubyTodo,@Spell
-if !exists("ruby_no_comment_fold")
+if !exists("ruby_no_comment_fold") && s:foldable('#')
   syn region rubyMultilineComment start="^\s*#.*\n\%(^\s*#\)\@=" end="^\s*#.*\n\%(^\s*#\)\@!" contains=rubyComment transparent fold keepend
   syn region rubyDocumentation	  start="^=begin\ze\%(\s.*\)\=$" end="^=end\%(\s.*\)\=$" contains=rubySpaceError,rubyTodo,@Spell fold
 else
@@ -315,7 +464,11 @@ syn match  rubySymbol		"\%([{(,]\_s*\)\@<=[[:space:],{]\l\w*[!?]\=::\@!"hs=s+1,h
 syn match  rubySymbol		"[[:space:],{(]\%(\h\|[^\x00-\x7F]\)\%(\w\|[^\x00-\x7F]\)*[!?]\=:[[:space:],]\@="hs=s+1,he=e-1
 
 " __END__ Directive
-syn region rubyData matchgroup=rubyDataDirective start="^__END__$" end="\%$" fold
+if s:foldable('__END__')
+  syn region rubyData matchgroup=rubyDataDirective start="^__END__$" end="\%$" fold
+else
+  syn region rubyData matchgroup=rubyDataDirective start="^__END__$" end="\%$"
+endif
 
 hi def link rubyClass			rubyDefine
 hi def link rubyModule			rubyDefine