Well, in the true spirit of open source software, another pair of eyes found a bug. utassert.ieqminus is missing the following line:

dbms_sql.bind_variable(cur, ':retval', ival);

which should occur after:

DBMS_SQL.PARSE (cur, v_block, DBMS_SQL.NATIVE);

This is for Oracle 7.3 (yes, I'm one of the last few pariahs). Steven, if you want me to send a patch, I'd be glad to.