Behavior of Scalar::Util::looks_like_number in Perl

Question

I am trying to find out if an input is number or string. I came across looks_like_number and cannot understand the values it returns.

use warnings;
use Scalar::Util qw(looks_like_number);

my $name = 11;
print looks_like_number ($name);

This code prints 1 if $name contains a string and a static number if $name contains an integer (i.e. 4352 for each integer).

I am using Perl on Windows.

Answer 1

You forgot to ask a question! Here are two possibilities.

Why doesn't it always return the same value for true?

Why not? It returns a true value as documented. It makes no difference which true value it is.

What is the value returned?

If the scalar contains a string, it uses grok_number which has specific document return values.

The type of the number is returned (0 if unrecognised), otherwise it is a bit-ORed combination of IS_NUMBER_IN_UV, IS_NUMBER_GREATER_THAN_UV_MAX, IS_NUMBER_NOT_INT, IS_NUMBER_NEG, IS_NUMBER_INFINITY, IS_NUMBER_NAN (defined in perl.h).

Otherwise, it uses

SvFLAGS(sv) & (SVf_NOK|SVp_NOK|SVf_IOK|SVp_IOK)

You can't tell which of the two was used, so you can't ascribe meaning to the value, which is why it's undocumented.