#!/usr/bin/perl
use strict;
use Benchmark qw( cmpthese );

foreach my $file qw ( /dev/null /usr/share/dict/words /etc/passwd ) {
    open my $IN1, '<', $file or die "could not open $file";
    my @list = <$IN1>;
    seek( $IN1, 0, 0 );
    print "$file\n";
    cmpthese(
        -5,
        {
            for_list => sub {
                my %counts = ();
                ++$counts{$_} for @list;
                die unless keys %counts == @list;
            },
            while_list => sub {
                my $x      = 0;
                my %counts = ();
                ++$counts{$_} while defined( $_ = $list[ $x++ ] );
                die unless keys %counts == @list;
            },
            for => sub {
                seek( $IN1, 0, 0 );
                my %counts = ();
                ++$counts{$_} for <$IN1>;
                die unless keys %counts == @list;
            },
            while => sub {
                seek( $IN1, 0, 0 );
                my %counts = ();
                ++$counts{$_} while <$IN1>;
                die unless keys %counts == @list;
            },
            whyfor => sub {
                seek( $IN1, 0, 0 );
                my %counts = ();
                for ( ; defined( $_ = <$IN1> ) ; ) { ++$counts{$_}; }
                die unless keys %counts == @list;
            },
        }
    );
}