That said, wrapping one particular library-based implementation of a priority queue to work on standard Perl SVs would be very interesting, and quite possibly useful, too.

That would be the idea -- something along the lines of a priority_queue<SV*,vector<SV*>,comparison_func> . Making it "nice" would require it being possible to pass a block of Perl code in as the comparison function (a la sort), which completely blows the inlining. Standard comparisons (e.g. string and numeric greater- and less-than) could still be specified as constants passed to the constructor, and implemented in pure C for speed. It would be interesting to see how much faster this would be than the Perl-only versions.

/s