Punkish symbolic expression parser

symbolic.rb

def parse_symbolic(text)
	#  Return nested list of symbols as parsed from input S-expr
	#
	#  text -- string with an S-expr
	#
	lexeme = /(?<quote_run>(?<quote>['"])(?<content>.*)\k<quote>(?<!\\))|(?<whole_word>\w+)|(?<bracket>[()])/

	text.strip!
	text.gsub!(lexeme) { |match|
		first_nonempty_index = Regexp.last_match.captures.index { |x| not x.nil? }
		case lexeme.names[first_nonempty_index]
		when 'quote_run'
			":#{match[1...-1].inspect},"
		when 'whole_word'
			":#{match},"
		when 'bracket'
			{'(' => '[', ')' => '],'}[match]
		end
	}
	text.chomp! ','
	eval text
end