use File::Slurp;
use Benchmark qw(cmpthese);

cmpthese(-2, { fs => sub { $x = read_file "foo" },
               is => sub { $x = is("foo"); }
             });

sub is { local (@ARGV, $/) = $_[0]; <> };

##</code><code>##

$ perl -e 'print "x"x500' > foo
$ perl benchmark
      Rate   fs   is
fs 30210/s   -- -33%
is 44886/s  49%   --

$ perl -e 'print "x"x5_000' > foo
$ perl benchmark
      Rate   fs   is
fs 27499/s   -- -26%
is 37057/s  35%   --

$ perl -e 'print "x"x50_000' > foo
$ perl benchmark
      Rate   is   fs
is 11275/s   -- -14%
fs 13094/s  16%   --

$ perl -e 'print "x"x500_000' > foo
$ perl benchmark
    Rate   is   fs
is 277/s   -- -15%
fs 325/s  17%   --

$ perl -e 'print "x"x5_000_000' > foo
$ perl benchmark
     Rate   is   fs
is 29.5/s   -- -17%
fs 35.6/s  21%   --