An interactive source commenter for Prolog programs

Prolog meta-circular interpreters, i.e., interpreters for Prolog written in Prolog, perform at least two operations on an object program - they parse it and execute its instructions. There is a useful variant of the meta-circular interpreter, the meta-circular parser, which as its name suggests, parses an object program without executing its instructions. The value of such a parser is that it provides an elegant means to modify Prolog source code. As the object program is parsed, new information in the form of additional instructions, comments, etc., can be selectively inserted.