Do I misunderstand the question or will the following not work?

Edit: Ok, I misunderstand the nature of the problem as noted by LanX in Re^2: Distiguishing arguments: number-strings vs real integer... My apologies.

#!/usr/bin/perl
use strict;
use warnings;
#use Data::Dump qw/pp dd/;

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

sub is_string {
    my $arg = $_[0];
    warn "$arg looks like number \n$&\n\n\n"
      if $arg =~ /(\d+)/;
}


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

my $n=1;
my $s="42";
my $s1="this contains the number 143";
my $s2 = "Awierd123number";

is_string($n);
is_string($s);
is_string($s1);
is_string($s2);

$n.="";                                 # cast to string
$s+=0;                                    # cast to number
is_string($n);
is_string($s);
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