#!/usr/bin/perl -w

use strict;
use warnings;

print isNumber("abc");   # returns 0
print "\n";
print isNumber("123");   # returns 1
print "\n";


sub isNumber
{
  @_ or return 0;
  my $N = shift;
  defined $N or return 0;
  my $R = 1;
  {
    local $SIG{__WARN__} = sub { $R = 0; };
    $N = int($N);
  }
  return $R;
}