#!/usr/bin/perl

use warnings;
use strict;
use Data::Dumper;
   
my @array = ( "APPLE", "ORANGE", "PEACH",         # Use this for the ORDER
           "GRAPE", "BANANA", "PINEAPPLE" );   
   
my @subset = ( "PINEAPPLE", "GRAPE", "ORANGE", "APPLE" );   # A required subset but NOT
                                               # in the required order
   
my @results = ();                                 # The subset with its elements in the 
                                               # same order as the 'reference' array

# ---- Method 2: Using hash

my %indexes;
my $index = 0;

map {
	$indexes{ $_ } = $index;
	$index ++; 
	} @array;

printf "  Index of element '$_' is: %d\n", $indexes{ $_ } for @subset;

my @tmp = ();
foreach my $check ( @subset ){
	my( $index ) = $indexes{ $check };
	push( @tmp, $index );
}

my @index_list = sort {$a <=> $b} @tmp;  # Sort the index values numerically
@results = @array[@index_list];       # Slice the index items out of '@array'

print "Method 2 (uses hash):\n";
print Dumper(@results);
print "\n";