I've been playing with a little grammar here to parse SQL "CREATE TABLE" syntax: 
my $grammar = q{
   startrule:              create_table_syntax
   create_table_syntax:    'CREATE TABLE' '(' column_definition(s /,/)
+ ')'
   column_definition:      column_name data_type column_attributes(?)
   column_name:            /\w+/
   data_type:             "INT" | "VARCHAR"
   column_attributes:     key_or_not_null
   key_or_not_null:       primary(?) 'KEY'
}

[download]
At the moment I'm experimenting with AUTOSTUB to get the key_or_not_null bit working. In BNF it looks like: 
<key_or_not_null_spec> ::= 
  [PRIMARY] KEY 
| NOT NULL [WITH DEFAULT]

[download]
As I understand it, the square braces around PRIMARY indicate that it can be matched "zero or one" times. So I tried "primary"(?) in PRD grammar and that bombed. Now I'm trying primary(?) with AUTOSTUB turned on and that's bombing too. I really don't want to have to make a subrule that just says: 
primary:    'primary'

[download]
But I don't really like the idea of using AUTOSTUB either - it seems kludgy. Ideally I want to be able to say "match this literal string zero or one times". Should I use a regex? Or is there some PRD grammar wisdom that I'm missing?

--
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Ash OS thrakatulk, agh burzum-ishi krimpatul!
Uzg-Microsoft-ishi amal fauthut burguuli.

In reply to Parse::RecDescent and AUTOSTUB by hagus

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