#!/usr/bin/perl -w
use strict;

my $test = -413;
print "$test is ok\n" if numeric( $test );

sub numeric {
    my $number = shift;
    return 0 if ! $number;
    my $first = substr( $number , 0 , 1 );
    $number = substr($number, 1) if $first eq '-';
    return 1 if $number =~ /^[1-9]\d+?$/;
    return 0;
}