#!/usr/bin/perl

use strict;
use warnings;
use IO::Tee;

open my $log, '>stdout.log' or warn "Can't write logfile: $!";
my $tee = new IO::Tee(\*STDOUT, $log);

# Use it like a file handle
print $tee "Just another perl hacker,\n";

# Use the print method of the IO::Tee object
$tee->print("Just another perl monk.\n");
$tee->flush;

__END__
Output:
C:\S\Test>iotee.pl
Just another perl hacker,
Just another perl monk.

C:\S\Test>type stdout.log
Just another perl hacker,
Just another perl monk.