#!/usr/bin/perl -l
use strict;
use warnings;

my @fileone = qw/123456 123457 123458/;
my @filetwo = ("123456 foo",
        "123456 bar",
        "123457 foobar",
        "123455 this wouldn't be printed to new file"
        );


foreach my $pattern (@fileone) {
    foreach my $line (@filetwo) {
        if ($line =~ /^$pattern/) {
            print $line;
        }
    }
}