unsigned char *lexemePtr,	/* Write code of parsed lexeme to this
				 * storage. */
    Tcl_Obj **literalPtr)	/* Write corresponding literal value to this
				   storage, if non-NULL. */
{
    const char *end;
    int scanned;
    Tcl_UniChar ch = 0;
    Tcl_Obj *literal = NULL;
    unsigned char byte;

    if (numBytes == 0) {
	*lexemePtr = END;
	return 0;
    }

     * We reject leading underscores in bareword.  No sensible reason why.
     * Might be inspired by reserved identifier rules in C, which of course
     * have no direct relevance here.
     */

    if (!TclIsBareword(*start) || *start == '_') {
	if (Tcl_UtfCharComplete(start, numBytes)) {
	    scanned = TclUtfToUniChar(start, &ch);
	} else {
	    char utfBytes[4];

	    memcpy(utfBytes, start, numBytes);
	    utfBytes[numBytes] = '\0';
	    scanned = TclUtfToUniChar(utfBytes, &ch);
	}
	*lexemePtr = INVALID;
	Tcl_DecrRefCount(literal);
	return scanned;
    }
    end = start;
    while (numBytes && TclIsBareword(*end)) {