I want to find out if a function is called with an integer or a string containing an integer.

Perl tries to hide what the scalar internally is, but Devel::Peek can be used here, the flag IOK shows an integer, POK a string.

looks_like_number() is no help here, I want the exact opposite.

Is there a more elegant way than catching and parsing the output of Dump?°

NB: Using PerlGuts optree vodoo is considered helpful but not more elegant ... ;)

use strict;
use warnings;
use Data::Dump qw/pp dd/;

use Scalar::Util qw/looks_like_number/;
use Devel::Peek;

sub is_string {
    Dump($_[0]);
    warn "$_[0] looks_like_number\n\n\n"
      if looks_like_number($_[0]);
}


is_string(1);
is_string("42");

my $n=1;
my $s="42";


is_string($n);
is_string($s);

$n.="";                                 # cast to string
$s+=0;                                  # cast to num
is_string($n);
is_string($s);
[download]

SV = IV(0x228e98) at 0x228ea8
  REFCNT = 1
  FLAGS = (PADTMP,IOK,READONLY,pIOK)
  IV = 1
1 looks_like_number


SV = PV(0x24d378) at 0x245af8
  REFCNT = 1
  FLAGS = (PADTMP,POK,READONLY,pPOK)
  PV = 0x22e078 "42"\0
  CUR = 2
  LEN = 16
42 looks_like_number


SV = IV(0x28ae40) at 0x28ae50
  REFCNT = 1
  FLAGS = (PADMY,IOK,pIOK)
  IV = 1
1 looks_like_number


SV = PV(0x3bd068) at 0x28a6a0
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK)
  PV = 0x26a1078 "42"\0
  CUR = 2
  LEN = 16
42 looks_like_number


SV = PVIV(0x234c40) at 0x28ae50
  REFCNT = 1
  FLAGS = (PADMY,POK,pPOK)
  IV = 1
  PV = 0x26a1048 "1"\0
  CUR = 1
  LEN = 16
1 looks_like_number


SV = PVIV(0x234c58) at 0x28a6a0
  REFCNT = 1
  FLAGS = (PADMY,IOK,pIOK)
  IV = 42
  PV = 0x26a1078 "42"\0
  CUR = 2
  LEN = 16
42 looks_like_number
[download]

°) which involves redirecting STDERR ... Yuck!!!