Re: when $$s =~ m/\G.../gc is too verbose

[radiantmatrix]

Why not just store $$s in a local copy of $_?

#Either
local $_ = $$s;

#Or
s//$$s/; #tricky.. ;-)

Actually, in this case, I'd be tempted to alter your approach altogether and use a regex table.

sub lexer {
   my ($parser) = shift;
   my $s = $parser->YYData->{INPUT};
   
   # I don't get your line: 'm/\G\s+/gc;  skip any spaces'
   my %dispatch = (
                    INT  => qr/\G(\d+)/gc, 
                    ID   => qr/\G([A-Z]\w*)/gc,
                    #.. and so on ..
                  );
   
   while (my ($key, $regex) = each %dispatch) {
      return ($key, $1) if $$s =~ $regex;
   }
}

[Corion]

Your second solution is no solution:

$_ = '!';
$s = \'No';
s//$$s/;
print;

You'd need to empty out $_ first, so the local $_ is the way.

[radiantmatrix]

Absolutely. That's the tricky part. ;-) It will work when $_ is undefined, but not otherwise. Of course, you could always change it to s/.*/$$s/, but still not advisable. More of an obfu trick...

[stefp]

About the copy: before even thinking about positions in strings, using a string copy is a no-no. Copying the string to be parsed for each token is madness.

About a table for lexing : this is irrelevant to the discussion. Also, lexing can be more complex than matching. Yes, one can insert regular code in regex but that the sign that a table based lexing is not appropriate.

As I said tye, using for is the right way to alias to $_. I don't like it because in the programming space, for is a loop... for me. :)

In the natural language space, well, English is not my first language.

So to paraphrase Churchill, for is the worst solution, but it is the only one.

Hopefully, like said TimToady, Perl6 will be cleaner.