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

#Either
local $_ = $$s;

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

[download]

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;
   }
}

[download]
<-radiant.matrix->
A collection of thoughts and links from the minds of geeks
The Code that can be seen is not the true Code
I haven't found a problem yet that can't be solved by a well-placed trebuchet

In reply to Re: when $$s =~ m/\G.../gc is too verbose by radiantmatrix
in thread when $$s =~ m/\G.../gc is too verbose by stefp

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