#!/usr/bin/perl -w

use strict;

sub i_am_a_number {
    shift;
    no warnings; # += 0 on a string sets off a warning

    # make sure that zero is counted as a number
    # ($_ += 0) alone fails on zero.
    if (/^\d+$/ || ($_ += 0)) {
        return 1;
    }
    return 0;
}

#############################################################
# take the sub on a test spin
my @list = (035, 35, +19, 12, "045", -2, 5.5, 0, -34.530, "hi!");

for (@list) {
    if (i_am_a_number($_)) {
        print "$_ is a number!\n";
    } 
}