#! perl
use strict;
use warnings;

my $filename = 'test.txt';
open(my $fh, '>', $filename) or die "Cannot open file '$filename' for writing: $!";
print $fh "The quick brown fox jumped over the unfortunate dog.";
seek $fh, 0, 0;
print $fh "The final output.";
close($fh) or die "Cannot close file '$filename': $!";

##</code><code>##

The final output.ox jumped over the unfortunate dog.