I agree—this looks like an issue in Tcl/Tk, because the Tk Aqua code is where autorelease pools are being handled and presumably can cause errors relating to that. (Though Perl could still be doing something Tcl doesn't like.) Hopefully some specific actions that cause this error can be identified in order to diagnose this further. Quite a few changes are still being made to Tk Aqua. Has this already been reported anywhere else?