grammar problems

[Jonas Wolf]

Hello,

I recently downloaded the Parse::RecDescent package to parse
boolean queries. I have several questions, not necessarily about
the package itself, but rather about my grammar. 

I am currently using the following grammar:

my $grammar = q
{
        <autotree>
        disj      : qualif(?) conj disjRec(s?)
         disjRec  : disjOp conj
        conj      : term conjRec(s?)
         conjRec  : conjOp term
        term      : brack | phrase | ident
        brack     : '(' disj ')'
        phrase    : '"' ident(s?) '"'
        ident     : /[a-zA-Z0-9]+/i
        qualif    : ident '='
        conjOp    : /AND/i
        disjOp    : /OR/i
};

I have several problems with this.

Firstly, the precedence isn't quite what I want in 'qualif'. I would
like 'ident' to bind tightly to whatever comes next to it. Currently
it seems to associate it with the whole 'disj' that comes after.

Secondly, I would like the 'conjOp' operator to be optional, and that
the parser recognises this. This means a query for 'a b' would be
interpreted as 'a AND b'. I tried replacing the conjOp rule with
'conjOp : /AND/i | ""', but this does not work, as now a query 
'a AND b' is interpreted as 'a AND and ...'.

Any help would be appreciated.

Thanks, Jonas.