Curious. I ran your benchmark and got a few warnings about "Parentheses missing around "my" list at (eval 42) line 3.", which I tracked down to the my $char in sysread test. So I stuck in the brackets expecting the absence of the warning generation to speed that case up a tad. To my surprise it doesn't. It slows it down a tad. It's consistant, but I can't explain why.

For variety, if the file is less than a couple of hundred megs, slurping the whole thing and using substr to iterate the chars is a fair bit quicker.

#!/usr/bin/perl

#! perl -slw
use strict;

use Benchmark qw /cmpthese/;
use Fcntl     qw /:DEFAULT :seek/;

our $file = $ARGV[0];

sysopen our $fh1 => $file, O_RDONLY or die $!; binmode $fh1;
open    our $fh2 => $file           or die $!; binmode $fh2;
open    our $fh3 => $file           or die $!; binmode $fh3;
sysopen our $fh4 => $file, O_RDONLY or die $!; binmode $fh4;

our ($c1, $c2, $c3, $c4) = (0, 0, 0, 0);

cmpthese -5 => {
    sysread  => 'sysseek $fh1 => 0, SEEK_SET or die;
                 $c1 = 0;
                 $c1 ++ while sysread $fh1 => my( $char ), 1',
    readline => 'seek $fh2 => 0, SEEK_SET or die;
                 local $/ = \1;
                 $c2 = 0;
                 $c2 ++ while defined (my $char = <$fh2>)',
    getc     => 'seek $fh3 => 0, SEEK_SET or die;
                 $c3 = 0;
                 $c3 ++ while defined (my $char = getc $fh3)',
    substr   => 'seek $fh4 => 0, SEEK_SET or die;
                 my( $char, $data );
                 sysread( $fh4, $data, -s $file );
                 $c4 = length( $data );
                 $char = substr( $data, $_, 1 )  for 0 .. $c4',

};
print "$c1 : $c2 : $c3 : $c4";

die '$c1 is empty' unless $c1;
die '$c2 is empty' unless $c2;
die '$c3 is empty' unless $c3;
die '$c4 is empty' unless $c4;
die 'Unequal'      unless $c1 == $c2 && $c2 == $c3 && $c3 == $c4;
__END__
P:\test>test fruit.exe
Parentheses missing around "my" list at (eval 42) line 3.
Parentheses missing around "my" list at (eval 44) line 3.
Parentheses missing around "my" list at (eval 46) line 3.
            Rate  sysread     getc readline   substr
sysread  0.931/s       --     -61%     -71%     -75%
getc      2.41/s     159%       --     -25%     -34%
readline  3.20/s     243%      33%       --     -13%
substr    3.67/s     294%      52%      15%       --
72192 : 72192 : 72192 : 72192
P:\test>test fruit.exe
            Rate  sysread     getc readline   substr
sysread  0.876/s       --     -63%     -73%     -76%
getc      2.35/s     168%       --     -26%     -36%
readline  3.20/s     265%      36%       --     -13%
substr    3.66/s     318%      56%      15%       --
72192 : 72192 : 72192 : 72192
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