#!/usr/bin/perl

use Benchmark 'cmpthese';
use warnings;

@array = (  'a'..'zz' );
$value = 'mz';
my $res;
my $position;

print "for(): ".traditional().
      "\tforeach: ".for_each().
      "\tmap: ".maptohash().
      "\tgrep_if: ".grep_if().
      "\tbinary search: ".bin_search().
"\n";

cmpthese ( 1000, { for_loop =>  '$res = traditional()',
                       map => '$res = maptohash()',
                  for_each => '$res = for_each()',
                   grep_if => '$res = grep_if()',
                bin_search => '$res = bin_search()',
                }
 );

sub traditional{
    for ($position=0; $position <= $#array; $position++) {
        last if ($array[$position] eq $value);
    }
    return $position;
}

sub for_each{
    for  our $position ( 0..$#array ) {
        last if ($array[$position] eq $value) ;
    }
    return $position;
}

sub maptohash{
    %indexed = map{ $array[$_], $_ } (0..$#array);
    return $indexed{$value};
}

sub grep_if{
    my  @res = grep {$array[$_] eq $value} (0..$#array);
   return @res[0];
}

sub bin_search {
    return BinSearch( $value, \&cmpFunc, \@array );
}

sub BinSearch
{
my ($target, $cmp) = @_;
my @array = @{$_[2]};

my $posmin = 0;
my $posmax = $#array;

return -0.5 if &$cmp (0, \@array, $target) > 0;
return $#array + 0.5 if &$cmp ($#array, \@array, $target) < 0;

while (1)
  {
  my $mid = int (($posmin + $posmax) / 2);
  my $result = &$cmp ($mid, \@array, $target);

  if ($result < 0)
    {
    $posmin = $posmax, next if $mid == $posmin && $posmax != $posmin;
    return $mid + 0.5 if $mid == $posmin;
    $posmin = $mid;
    }
  elsif ($result > 0)
    {
    $posmax = $posmin, next if $mid == $posmax && $posmax != $posmin;
    return $mid - 0.5 if $mid == $posmax;
    $posmax = $mid;
    }
  else
    {
    return $mid;
    }
  }
}

sub cmpFunc
{
my ($index, $arrayRef, $target) = @_;
my $item = $$arrayRef[$index];

return $item cmp $target;
}


 %perl foo.pl                                                             [10:49pm]
Scalar value @res[0] better written as $res[0] at foo.pl line 47.
for(): 363      foreach: 363    map: 363        grep_if: 363    binary search: 363
             Rate        map   for_loop    grep_if bin_search   for_each
map         200/s         --       -69%       -72%       -81%       -88%
for_loop    650/s       224%         --        -8%       -39%       -60%
grep_if     707/s       253%         9%         --       -33%       -57%
bin_search 1058/s       428%        63%        50%         --       -36%
for_each   1641/s       719%       153%       132%        55%         --