package Foo;
use strict;

use Class::Multimethods;
*Foo::new = \&_newFoo;

multimethod _newFoo => ('$')
 => sub {
     print "I'm constructor for Foo\n";
     bless {},$_[0];
 };
1;

## Foo.2pm
package Foo2;
use strict;

use Class::Multimethods;
*Foo2::new = \&_newFoo2;

multimethod _newFoo2 => ('$')
 => sub {
     print "I'm constructor for Foo2\n";
     bless {},$_[0];
 };
1;
## Now, it works as it should be. Of course with also other 
## overloaded methods like _newFoo('$','HASH'),_newFoo2('$','$')