#!perl

use strict;
use warnings;

my (@array, %hash);

sub push_item {
   # push_item(key => value)
   return 0
      if defined $hash{$_[0]};
   push @array, [$_[1], $_[0], scalar @array];
   $hash{$_[0]} = $array[-1];
   return 1;
}

sub swap_array {
   # swap_array(index1, index2)
   @array[$_[0], $_[1]] = @array[$_[1], $_[0]];
   ($array[$_[0]]->[2], $array[$_[1]]->[2])
      = ($array[$_[1]]->[2], $array[$_[0]]->[2]);
}

sub get_array_pos_by_key {
   # get_array_pos_by_key(key)
   return undef
      unless exists $hash{$_[0]};
   $hash{$_[0]}->[2];
}

sub get_hash_key_by_index {
   # get_hash_key_by_index(index)
   return undef
      unless $_[0] < @array;
   $array[$_[0]]->[1];
}

# populate

push_item('foo'    => 'bar');
push_item('joe'    => 'banana');
push_item('foe'    => 'friend');
push_item('gin'    => 'tonic');
push_item('ice'    => 'age');

print get_array_pos_by_key('gin'), "\n";
print get_array_pos_by_key('joe'), "\n";
print $hash{'gin'}->[0], ' ', $hash{'joe'}->[0], "\n";
print $array[3]->[0], ' ', $array[1]->[0], "\n";
swap_array(get_array_pos_by_key('gin'), get_array_pos_by_key('joe'));
print get_array_pos_by_key('gin'), "\n";
print get_array_pos_by_key('joe'), "\n";
print $hash{'gin'}->[0], ' ', $hash{'joe'}->[0], "\n";
print $array[3]->[0], ' ', $array[1]->[0], "\n";
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