'Course, that doesn't work when 'a' contains parentheses.

That gets us out of deciding how to spell Reg[eE]xp?|RE . . . Of course, then we have to decide what ref $re returns... :-)

I was trying not to mention backtracking. Which, of course, means that yours is 'righter' than mine, in a theoretical sense.

That should probably be written: no !@#$%^&*:@!semicolon

There are probably better ways to do that, but it would make the parser more complex. I do, occasionally, struggle feebly against complexity... :-)

/* This bit of chicanery makes a unary function followed by a parenthesis into a function with one argument, highest precedence. */

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