file-descriptor-check.pl

#!perl
use strict;
use warnings;

use IO::File;
my $fh = IO::File->new;
if ($fh->open("2012-03-30-091435.pl")) {
    warn $fh->fileno;
    $fh->close;
}

warn fileno(STDIN);
warn fileno(STDOUT);
warn fileno(STDERR);