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

my ($foo, $bar);

print '1: ', $foo eq $bar, "\n";    # Uninitialized warning. 
{ 
    no warnings qw( uninitialized ); 
    print '2: ', $foo eq $bar, "\n";    # No warnings emitted.
}

print '3: ', $foo eq $bar, "\n";    # Warns again.

##</code><code>##

((defined($x) && defined($y) && ($x eq $y))
     || (!defined($x) && !defined($y))

##</code><code>##

( defined($x && $y) and ($x eq $y) ) or not defined($x || $y)

##</code><code>##

defined($x&&$y)&&$x eq$y||!defined($x||$y)