use strict;
my $str = ':pseudo-class(value)[attribute~=value]#id.class > ::pseudo-element, element';
my $regex = qr/( *(((([a-zA-Z]+)|([.#](\w|\w+-+\w*)+)|(:(\w+(-\w+)+)(\([a-zA-Z0-9]+\))?)|(:{2}(\w+(-\w+)+))|(\*))(\[ *\w+ *(([\^$|~*]?= *)?((\w|\w+-+\w*)+|((\\') *.+ *(\\'))|((\\") *.+ *(\\"))|((') *.+ *('))|((") *.+ *("))))?( *\]))*)|(\[ *\w+ *(([\^$|~*]?= *)?((\w|\w+-+\w*)+|((\\') *.+ *(\\'))|((\\") *.+ *(\\"))|((') *.+ *('))|((") *.+ *("))))?( *\]))+)((([a-zA-Z]+)|([.#](\w|\w+-+\w*)+)|(:(\w+(-\w+)+)(\([a-zA-Z0-9]+\))?)|(:{2}(\w+(-\w+)+))|(\*))*(( +|( *[,~>+] *))(((([a-zA-Z]+)|([.#](\w|\w+-+\w*)+)|(:(\w+(-\w+)+)(\([a-zA-Z0-9]+\))?)|(:{2}(\w+(-\w+)+))|(\*))(\[ *\w+ *(([\^$|~*]?= *)?((\w|\w+-+\w*)+|((\\') *.+ *(\\'))|((\\") *.+ *(\\"))|(' *.+ *')|((") *.+ *("))))?( *\]))*)|(\[ *\w+ *(([\^$|~*]?= *)?((\w|\w+-+\w*)+|((\\') *.+ *(\\'))|((\\") *.+ *(\\"))|((') *.+ *('))|((") *.+ *("))))?( *\]))+))*)* *(?!.))/yp;
my $subst = '';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html