#!/usr/bin/perl
use strict;
sub test($);

test 'a';
test 'z';
test 'xyz';
test 'az';

sub test($) {
    my $s = shift;
    for my $c (split '', $s) {
        if ($c !~ /[xyz]/) {
            print "$s does not match\n";
            return;
        }
    }
    print "$s matches\n";
}