This is the putative patch for TIP#36. Note the diverging behaviour of command substitutions that return TCL_BREAK, which in this implementation causes no more characters to be added to the result string (and this gives a meaning to it distinct from TCL_CONTINUE, which is more useful when used to skip over a particular script.) Still to be done: * finish the TIP! * move the #defines to the right header file * create the right tcl.decls entry * write tests (especially that demonstrate the diverging capabilities.) * write documentation, both the update to subst.n and the new Tcl_SubstObj.3 Donal.