#!/usr/bin/perl

use strict;
use warnings;
use Benchmark qw(:all);

cmpthese(-3,
                    {
                        'Original' => \&test1,
                        'kral' => \&test2,
                      'BrowserUk' => \&test3,    
                        'kvale' => \&test4,
                    }
                 );

my @list = qw( pippo pluto foo Foo );

sub test4 {
    my $str_a = 'Foo';
    my $letter = substr $str_a, 0, 1;
    for my $str_b ( @list ) {
    next if $letter eq substr $str_b, 0, 1;
    expensive_function($str_a , $str_b);
    }
}

sub test3 {
    my %list; @list{ map{ substr $_, 0, 1 } @list } = ();

    my $str_a = 'Foo';                               
    my $first_char = substr $str_a, 0, 1;
    for my $str_b ( @list ) {                         
    next if exists $list{ $first_char };  
    expensive_function($str_a , $str_b);
    }
}

sub test2{
    my $str_a = 'Foo';
    my $letter = substr $str_a, 0, 1;
    for my $str_b ( @list ) {
    next if (ord($letter) == ord((split(//, $str_b))[0]));
    expensive_function($str_a , $str_b);
    }
}

sub test1 {
    my $str_a = 'Foo';                                # Can be any len
+gth
    for my $str_b ( @list ) {                         # Can be any num
+ber of items
    next if index($str_a, substr($str_b, 0, 1));  # Only change this
    expensive_function($str_a , $str_b);
    }
}
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