Rather than solving the problem of circular dependencies, Sort::Topological just insists you not have any. Take a look at the Graph module, which has a toposort function. That still doesn't solve detection, but it doesn't blow up:

$ perl -MGraph -e'my $g=Graph->new();$g->add_cycle(qw/foo bar baz/);$g
+->add_edge(qw/quux foo/);print $g->toposort()'
quuxbarbazfoo$
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You could detect cycles by, for each node, checking if there is a path to any of its predecessors. That will not scale well, but it can be done

Graph nodes can carry weights, which will allow the priority part of your problem. Properly set up, a minimum spanning tree, $G->MST_Kruskal, should give a solution.