#!/usr/bin/perl

use strict;
use warnings;

foreach (<DATA>) {
  chomp;
  print "$_ : ";
  if (/^(?:...)*(abc|xyz)/) {
    print "Match on $1\n";
  } else {
    print "No match\n";
  }
}

__DATA__
abcmmmmmm
mmmxyzmmm
mabcmxyzm