"diameter", "has_a_cycle" problems in Graph-0.76 module - Perl

Hello all,

I have some problems with these two functions in Graph : "diameter" and
"has_a_cycle".

"diameter" works only at the first time it's used. If then I added some
other vertices and edges, and call diameter again, it returns the
previous value, no matter how the graph is changed.

"has_a_cycle" should return true when there is a cycle in the graph,
and false if not. However, when there is no cycle, it returns
"uninitialized value" instead of false.

Thanks for help.