flags object from strings

[Kevin Ryde <user42 zip com au>]

Is there a way to make a Glib::Flags object, or rather a subclass like
Gtk2::Gdk::EventMask, from an array of elements like ['a','b','c']?
Which is to say, perl level access to gperl_convert_flags() basically.

I know an array is converted automatically on input to various funcs,
but I'd like to do some arithmetic setting and clearing elements, and
thought to use the flags object overloads, as long as one of my operands
is an object.