How do I tell if a variable has a numeric value in Perl?

Question

Is there a simple way in Perl that will allow me to determine if a given variable is numeric? Something along the lines of:

if (is_number($x))
{ ... }
         


        

Answer 1

Personally I think that the way to go is to rely on Perl's internal context to make the solution bullet-proof. A good regexp could match all the valid numeric values and none of the non-numeric ones (or vice versa), but as there is a way of employing the same logic the interpreter is using it should be safer to rely on that directly.

As I tend to run my scripts with -w, I had to combine the idea of comparing the result of "value plus zero" to the original value with the no warnings based approach of @ysth:

do { 
    no warnings "numeric";
    if ($x + 0 ne $x) { return "not numeric"; } else { return "numeric"; }
}