#! /usr/bin/perl -w
use strict;

my @testdata = qw (abc aabc cba cab bac bba cbc bbc abcdefg 0a2c3bc);

foreach (@testdata) {
	my $test = join '', sort split //, lc $_;
	$test =~ /[^a]*abc(?!c)[^c]*/ ? print "Matched $_\n" : print "Didn't match $_\n";