#!/usr.bin/perl -l

BEGIN { 
    $| = 1;
    $^W = 1;
}

use strict;
use autodie;
use warnings;

my $file = "file.txt";
1 while unlink $file;

use Tie::File;

my $o = tie my @lines, 'Tie::Tile', $file, memory => 0;
for (@lines) {
    $lines[2] = "something else is here now';
    print $lines[2];
    #line 3 is now "something else is here now".
}

END {
    undef $o;
    untie @lines;
    1 while unlink $file;
    #clears and empties everything.
}