_Tcl::__expression_parse

Given a string (or String), return a single stack that contains the work to be done. This stack can then be passed to __expression_interpret to actually invoke the items on the stack.

Uses the standard two arg return - if TCL_ERROR is returned, then we return our error information back up the chain. If we return TCL_OK, however, then we're returning the invokable PMC.

_Tcl::__get_call_level

Given a pmc containing the tcl-style call level, return an int-like pmc indicating the parrot-style level, and an integer with a boolean 0/1 - was this a valid tcl-style level, or did we get this value as a default?