How can I use the perl6 regex metasyntax, <foo regex>?

Question

In perl6 grammars, as explained here (note, the design documents are not guaranteed to be up-to-date as the implementation is finished), if an opening angle bracket is followed by an identifier then the construct is a call to a subrule, method or function.

If the character following the identifier is an opening paren, then it's a call to a method or function eg: <foo('bar')>. As explained further down the page, if the first char after the identifier is a space, then the rest of the string up to the closing angle will be interpreted as a regex argument to the method - to quote:

 <foo bar>

is more or less equivalent to

 <foo(/bar/)>

What's the proper way to use this feature? In my case, I'm parsing line oriented data and I'm trying to declare a rule that will instigate a seperate search on the current line being parsed:

#!/usr/bin/env perl6
# use Grammar::Tracer ;

grammar G {
    my $SOLpos = -1 ;   # Start-of-line pos

    regex TOP {  <line>+  }

    method SOLscan($regex) {
        # Start a new cursor
        my $cur = self."!cursor_start_cur"() ;

        # Set pos and from to start of the current line
        $cur.from($SOLpos) ;
        $cur.pos($SOLpos) ;

        # Run the given regex on the cursor
        $cur = $regex($cur) ;

        # If pos is >= 0, we found what we were looking for
        if $cur.pos >= 0 {
            $cur."!cursor_pass"(self.pos, 'SOLscan')
        }

        self
    }

    token line {
        { $SOLpos = self.pos ; say '$SOLpos = ' ~ $SOLpos }
        [
        || <word> <ws> 'two' { say 'matched two' }  <SOLscan \w+> <ws> <word>
        || <word>+ %% <ws>    { say 'matched words' }
        ]
        \n
    }

    token word  {  \S+  }
    token ws    {  \h+  }
}

my $mo = G.subparse: q:to/END/ ;
hello world
one two three
END

As it is, this code produces:

$ ./h.pl
$SOLpos = 0
matched words
$SOLpos = 12
matched two
Too many positionals passed; expected 1 argument but got 2
  in method SOLscan at ./h.pl line 14
  in regex line at ./h.pl line 32
  in regex TOP at ./h.pl line 7
  in block <unit> at ./h.pl line 41
$

Line 14 is $cur.from($SOLpos). If commented out, line 15 produces the same error. It appears as though .pos and .from are read only... (maybe :-)

Any ideas what the proper incantation is? Note, any proposed solution can be a long way from what I've done here - all I'm really wanting to do is understand how the mechanism is supposed to be used.

Answer 1

It does not seem to be in the corresponding directory in roast, so that would make it a "Not Yet Implemented" feature, I'm afraid.