#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dumper;

# use fixed values for repeatable tests
my @input = 1..100;
my @valuesToMatch = map {$_*14} 1..10;
my @expectedOutput = (14,28,42,56,70,84,98);
print Dumper(\@valuesToMatch);

# precompute what can be precomputed
# for the regex approach
my $regex_str = join '|', map {quotemeta}
	sort { length $b <=> length $a } @valuesToMatch;
my $regex = qr/(?:\A|\0)($regex_str)(?:\z|\0)/;
# for the hash approach
my %matchtbl = map {$_=>1} @valuesToMatch;

# the different implementations, in a dispatch table
my %subs = (
	hash => sub {
		my @matches = grep {$matchtbl{$_}} @input;
		return @matches;
	},
	regex => sub {
		my @matches = join("\0", @input) =~ /$regex/g;
		return @matches;
	},
	grep => sub {
		my @matches;
		for my $in (@input) {
			push @matches, $in
				if grep {$in==$_} @valuesToMatch;
		}
		return @matches;
	},
);

# check to make sure our implementations are all working
use Test::More;
for my $sub (sort keys %subs) {
	my @results = $subs{$sub}->();
	is_deeply \@results, \@expectedOutput, $sub
		or diag explain \@results;
}
done_testing;

# now benchmark the implementations
use Benchmark qw/cmpthese/;
cmpthese(-3, \%subs);

##</code><code>##

$VAR1 = [ 14, 28, 42, 56, 70, 84, 98, 112, 126, 140 ];
ok 1 - grep
ok 2 - hash
ok 3 - regex
1..3
          Rate  grep regex  hash
grep   33107/s    --  -49%  -85%
regex  65160/s   97%    --  -70%
hash  218506/s  560%  235%    --