static Tcl_Size
ParseLexeme(
    const char *start,		/* Start of lexeme to parse. */
    Tcl_Size numBytes,		/* Number of bytes in string. */
    unsigned char *lexemePtr,	/* Write code of parsed lexeme to this
				 * storage. */
    Tcl_Obj **literalPtr)	/* Write corresponding literal value to this
				   storage, if non-NULL. */
				 * storage, if non-NULL. */
{
    const char *end;
    int ch;
    Tcl_Obj *literal = NULL;
    unsigned char byte;

    if (numBytes == 0) {