Extending XOTcl Attribute slot

Hi,
I am trying to extend the XOTcl Attribute slot but I find that I
cannot declare methods with just no arguments as I run into some kind
of collision with Attribute definition.

I think I can explain it better by means of an example: let us try to
have a list Attribute that does pop !

Class AttL -superclass Attribute

AttL instproc init {
args
} {
next
my multivalued true
}

AttL instproc pop {
obj
var
} {
set res [lindex [$obj $var] end]
lreplace [$obj $var] end end
return $res
}

Class A -slots {
AttL MyList
}

A a
a MyList add 5
a MyList add 6
puts [a MyList pop]

I was expecting the 5 to appear (add is adding at the beginning) but
instead I got just pop.

Does this mean I cannot define a method as intended with no arguments
apart from the context?

I would appreciate any suggestions on this.

Thanks !

jima

.