#!/usr/bin/perl
# Regular expression to check the postcode (NL)

use strict;
use warnings;

while (<DATA>) {
  chomp;
  my $postcode =$_;
  if ($postcode =~ m{^[0-9]{4,4}\s[A-Z]{2,2}}) {
    print "postcode $postcode ok!\n";
  }   
  else {
    print "postcode $postcode not ok!\n";
  }  
}

exit 0;

__DATA__
1001 AA
1001 aa
1001AA
1001aa
100G AA
1001 Aa
-100 AA