#!/usr/bin/perl

use Benchmark;
use strict;

timethese(10, { 'linebyline' => \&linebyline, 'chunk' => \&chunk });

sub linebyline {
   open(FILE, "file");
   while(<FILE>) { }
   close(FILE);
}

sub chunk {
   my($buf, $leftover, @lines);

   open(FILE, "file");

   while(read FILE, $buf, 10240) {
      $buf = $leftover.$buf;
      @lines = split(/\n/, $buf);
      $leftover = ($buf !~ /\n$/) ? pop @lines : "";
      foreach (@lines) { }
   }

   close(FILE);
}

Benchmark: timing 10 iterations of chunk, linebyline...
     chunk: 60 wallclock secs (55.20 usr +  3.48 sys = 58.68 CPU)
linebyline: 95 wallclock secs (91.67 usr +  2.16 sys = 93.83 CPU)