package MyOleTypeLib;

use Moose::Util::TypeConstraints;

sub isDictionary {
    my $val = shift;
    return 0 
        unless $val->isa('Win32::OLE');
    my @lst = Win32::OLE->QueryObjectType($val);
    return ( $lst[0] eq 'TSATLLib'      # different for real ...
            and $lst[1] eq 'ITSEnt');   # ... VBS dictionary
}

subtype 'Dictionary', 
    as      'Object',
    where   { isDictionary($_) },
    message { "$_ is not a OLE-Dictionary!"};

# in my Class:

class Dictionary {
  has '_DictObj' => ( 
	   isa      => 'Dictionary',
  ...