perl6 grammar question

test031.pl6

I'm trying to use perl6 and his grammar feature. The following code works well and help me to recognize instructions starting by '\' and ending by ' ;' :
__________________________________________
$ cat test031.pl6
#!/opt/rakudo-star-2016.10/bin/perl6
use v6;

grammar SQLP {
  rule  TOP     {^^<cmdsqlplist> }
    rule cmdsqlplist  { <cmdsqlp> * }
    rule cmdsqlp  { :r  [^^'\\' <ff> ';'] }
    token ff     { <-[\\;]>* }
}


my $ctl = q:to/FIN_INI/;
\echo coucou   ;
\echo coucou  ;
\set toto titit  ;
FIN_INI


say $ctl;
say "-------";
my $scr = SQLP.parse($ctl);
say "scr:$scr";
say "-------";

$ perl6 test031.pl6
\echo coucou   ;
\echo coucou  ;
\set toto titit  ;

-------
scr:\echo coucou   ;
\echo coucou  ;
\set toto titit  ;

-------


My question is I'd like to recognize instructions starting by '\' and ending by « end of line ». I tried to replace ' ; ' by $$ ( I also tried  <:Zl> ) in my previous  code but without any success :

 $ cat test032.pl6
#!/opt/rakudo-star-2016.10/bin/perl6
use v6;

grammar SQLP {
  rule  TOP     {^^<cmdsqlplist> }
    rule cmdsqlplist  { <cmdsqlp> * }
    rule cmdsqlp  { :r  [^^'\\' <ff> $$] }
    token ff     { <-[\\]>* }
}


my $ctl = q:to/FIN_INI/;
\echo coucou   
\echo coucou  
\set toto titit  
FIN_INI


say $ctl;
say "-------";
my $scr = SQLP.parse($ctl);
say "scr:$scr";
say "-------";

$ perl6 sql032.pl6
\echo coucou   
\echo coucou  
\set toto titit  

-------
Use of uninitialized value $scr of type Any in string context.
Methods .^name, .perl, .gist, or .say can be used to stringify it to something meaningful.
  in block <unit> at sql032.pl6 line 22
scr:
-------


I don't understand why using $$ instead of ' ;' is not correct. Could you, please, help me ?