#!/usr/bin/env perl
use 5.010; use strict; use warnings;

my $field = 'Apt.302. 123-4567. 4021'; # from database record
$field = " $field ";                   # pad it
while($field =~ /[^\d-](\d\d\d\d?)[^\d-]/g){
    say "Apartment: $1";
}