#!/usr/bin/perl 

use strict;
use warnings;

sub same_sign {
    my $i=0;
    printf( "%2d %2d => ", $_[0], $_[1] );
    s/-/$i=$i+1;/e for @_; 
    $i!~/1/;
}

my $val = [ [ 1, 2 ], [ -1, 2 ], [ 1, -2 ], [ -1, -2 ] ];

for ( 0 .. $#{$val} ) { 
    my ( $x, $y ) = ( $val->[$_][0], $val->[$_][1] );
    print same_sign( $x, $y ) ? '' : 'not ', "same sign\n";
}

##</code><code>##

 1  2 => same sign
-1  2 => not same sign
 1 -2 => not same sign
-1 -2 => same sign