Perl IFs skipping branches

This one is a challenge, I am trying Perl for the first time ever and this is a basic calculation script I want to use in my teaching (replicated in different languages to show syntactical differences). I am becoming unstuck on the IFs used to try and prevent div by zero errors in the divide procedure and similar in the subtract procedure, the interpretor jumps straight to ELSE:

Code:[aaron@orion perl]$ perl mini_calc.pl
20
Error!1
25
0This is my script below:
Code:#!/usr/bin/perl

use warnings;

sub add{
$a = $_[0];
$b = $_[0];
return $a+$b
}

sub subtract{
$c = $_[0];
$d = $_[0];

if($c <=> $d){
return $c-$d;
}

elsif($d <=> $c){
return $d-$c;
}

else{
print "Error!";
}
}

sub multiply{
$e = $_[0];
$f = $_[0];
return $e*$f;
}

sub divide{
$g = $_[0];
$h = $_[0];

if(($g || $h) != 0)
{
if($g <=> $h){
return $g/$h;
}

elsif($h <=> $g){
return $h/$g;
}
}

elsif(($g || $h) == 0){
print "Div by zero error!";
}
}
# call function and then print result to console
$add = add(10,10);
printf $add."\n";

$subtract = subtract(70,10);
printf $subtract."\n";

$multiply = multiply(5,5);
printf $multiply."\n";

$divide = divide(10,5);
printf $divide."\n";If anyone has any pointers please I'd be ever so grateful.