#! perl
use strict;
use warnings;

my $file = 'test.txt';

open(my $fh, '>', $file)
    or die "Cannot open file '$file' for writing: $!";

use Tie::STDOUT
    print  => sub
    {
        print  @_;
        print  $fh '[', scalar localtime, ']: ', @_;
    },
    printf => sub
    {
        printf @_;
        print  $fh '[', scalar localtime, ']: ';
        printf $fh @_;
    };

print  "Perl is cool!\n";
printf "Pi is %f\n", atan2(1, 1) * 4;

close $fh
    or die "Cannot close file '$file': $!";