#!/usr/bin/perl -w
use strict;
my $input = "aa (bb cc) dd (ee (ff (gg) hh) jj) kk ((ll)) mm";
no strict 'vars';
# from $RE{balanced}{-parens=>'()'};
$REparens = qr/
	(?:(?:(?:[(](?:(?>[^)(]+)
	|(??{$REparens}))*[)]))
	|(?:(?!)))/x;

my $re = $REparens;	
use strict;

print "input: $input\n";
while ($input =~ /\G(\w+|$re)\s*/gc) {
	print "$1\n"
}
__END__
output:
aa
(bb cc)
dd
(ee (ff (gg) hh) jj)
kk
((ll))
mm