Parse::RecDescent - specifying dynamic subrule repetition

[leahymr]

Dear Monks, I beg your wisdom...

I am trying to parse a string for which I need to consume dynamically determined number of characters. Can P:RD be persuaded to do that?

Here is a simple example string:
s:5:"abcde"; -- the '5' is the number of characters in the string

Here's the hard part:
s:18:"s:10:"abcdefghij";"; -- the string can store other strings, so I can't just search for ";

I know that subrules can have repetition counts, but I can't get something like
String: 's: ' Count '"' Cdata($item{Count}) '";' to work

Here's the simplified grammar. Is there a way I can consume the number of characters specified by $item{Count}?

my $grammar = q{

    
    CompText:  Command(s)
    
    Command:
        String
      | Integer
    
    Array: 'a:' <commit> Count ':{' Command(s) '}'
        { $return = "a:$item{Count}:{" . join( '', @{$item[-2]}) . "}"
        }
    
    String: 
        's:' Count ':"' Array '";'
        { $return = "s:$item{Count}:\"" . join( '', @{$item{Array}}) .
+ "\";"
        }
          
      | 's:' Count ':"' Cdata_String '";'
        { $return = "s:$item{Count}:\"" . join( '', @{$item[-2]}) . "\
+";"
        }

      
    Cdata_String: Cdata(s?)
    
    Count: /\d+/
    
    Cdata: 
         /./
         
};

Thank you,
--Michael