#!/usr/bin/perl
use strict;
use warnings;
use Tie::File::Custom;

tie *fh, 'Tie::File::Custom', 'file.txt' or die "Unable to tie : $!";

(tied *fh)->LINES( 2  ); # Return 2 lines at a time
(tied *fh)->BUFF( 100 ); # Read 100 bytes at a time since we expect short lines

while ( <fh> ) {
    print $_, "-\n";
}