What I am trying to do here is to abstract away a very complex XSUB interface consisting of an iterator (here repersented by MyTie) over a C++ class (Dummy in the code below) as a tied array. I want to allow the user to iterate over the classes by a simple foreach. And while doing that, the user should really be able to use the overloaded operators of the Dummy class.

#!/usr/bin/perl

package Dummy;

use strict;
use warnings;

use overload '==' => \&iseq;
sub new  { return bless [ $_[1] ], $_[0];}
sub iseq { return $_[0]->[0] == $_[1]->[0] ;}

package MyTie;

use strict;
use warnings;
use Carp;

our $AUTOLOAD;

sub TIEARRAY {
  my $class = shift;
  return bless [ map { Dummy->new($_) } @_ ], $class;
}
sub FETCH     { $_[0]->[ $_[1] ]; }
sub FETCHSIZE { scalar @{$_[0]}; }
sub AUTOLOAD  { croak "Undefined method $AUTOLOAD called in " . __PACK
+AGE__;}

package main;

use strict;
use warnings;

use Data::Dumper;
use Devel::Peek;

tie my @arr, 'MyTie', 1,3,4;

for my $i (@arr){
  for my $j (@arr){
# uncomment this row and comment out the next one, and it works
#    if($i->iseq($j)){
    if($i == $j){
      print $i->[0] . " == " . $j->[0] . "\n";
    } else {
      print $i->[0] . " != " . $j->[0] . "\n";
    }
  }
}

exit 0;
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Curiously, I get the error:

Operation `0+': no method found, argument in overloaded package Dummy 
+at 5perltie.pl line 42.
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So Perl wants to force one of the arguments in ($i == $j) into numeric context. If I add the 0+ overloaded operator:

use overload '==' => \&iseq, '0+' => \#
...
sub num  { print "Someone wants me (" . $_[0]->[0] . ") in numeric con
+text\n"; }
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this is what I get:

Someone wants me (1) in numeric context
Someone wants me (1) in numeric context
1 == 1
1 != 3
1 != 4
Someone wants me (1) in numeric context
Someone wants me (3) in numeric context
3 == 1
3 == 3
3 != 4
Someone wants me (1) in numeric context
Someone wants me (4) in numeric context
4 == 1
4 != 3
4 == 4
[download]

Apparently, it works by also using fallback => 1 in this case, but it won't work in my case, since my complicated class won't let Perl default comparison operators work.

By the way, this is perl, v5.8.7 built for i486-linux-gnu-thread-multi.