How to determine if something is numeric?

[mifflin]

I need to determine if something is numeric.
By numeric I mean...
1. no alpha
2. no leading zeros ( 0001 or -0001 needs to be considered not-numeric)

here is what I came up with

use warnings;
use strict;

my $var = 'abc';
no warnings;
my $testvar = $var + 0;
use warnings;

if ($var eq $testvar) {
   print "$var is numeric\n";
}
else {
   print "oops, $var is NOT numeric\n";
}

Is this considered the right way to go about it? Is there a better way?