#!/usr/bin/perl

use strict;
use warnings;

while (<DATA>) {

   # 1
   # my @arr = split;
   # print if $arr[1] != $arr[3];

   # 2
   print if sub { $_[1] != $_[3] }->(split);
 
}

# 3
# while (@_ = <DATA> =~ /(\w+)\s+/g) {print "@_\n" if $_[1] != $_[3]}

__DATA__
foo 1000 bar 1000
foo 1000 bar 500

##</code><code>##

foo 1000 bar 500