#!/usr/bin/perl

use strict;
use warnings 'all';

my @vampire;

foreach my $s (1 .. shift) {
  LOOP:
    foreach my $t (1 .. $s) {
        my $prod = $s * $t;
        my $cat  = "$s$t";

        foreach my $d (0 .. 9) {
            next LOOP unless eval "\$prod =~ y/$d/$d/ ==
                                   \$cat  =~ y/$d/$d/";
        }
        push @vampire => [$prod, $s, $t];
    }
}

@vampire = sort {$a -> [0] <=> $b -> [0]} @vampire;

foreach my $vamp (@vampire) {
    printf "%4d * %4d = %8d\n" => @$vamp [1, 2, 0];
}