Another thing you should consider is representing the zip code as a string, not a numeric value. Unless you're doing some sort of math on zip codes, there's really no reason it has to be numeric. Also, as someone pointed out, international postal codes come in various formats. With postal codes stored as strings, your program could be more easily modified later on if it needs to handle those as well.
my $zip = "09876";
print "Zip is: '$zip'\n";