davido has already explained how Perl converts strings to numbers which should answer your question. However, I'll point out an improvement to your input function:

sub input
{
    print @_;
    my $r = <STDIN>;
    chomp $r;
    return $r;
}
[download]

That way, the input function does your chomping for you, and you don't need to litter chomp calls throughout your code.