key_or_not_null: ('primary')(?) 'key' |
                 'not' 'null' # if you put 'not null' then it won't gr
+ok things with two spaces
[download]

Also, there are other things to keep in mind:

1. By default (i.e. if you're not using autoaction) each item evaluates to the last object on its line. That means your 'key_or_not_null' will return 'KEY'.
2. Doing that ('primary')(?) thing still makes a new rule, it's jut that P::RD makes the rule for you (naming it 'anonymous_subrule_1_of_production_1_of_key_or_not_null' or something similar). This is because P::RD can't backtrack within a rule (so it can't backtrack if it doesn't match the word 'primary').

You probably want to use something like this:

key_or_not_null: m/primary|/i 'KEY'
[download]

• Using a regex with /i gives it proper case-insensitivity (as SQL is case-insensitive for its keywords)
• That won't fork off into a second subrule. Instead, $item[1] will be either 'primary' or '' to indicate the absence of the word 'primary'.

$"=$,,$_=q>|\p4<6 8p<M/_|<('=>
.q>.<4-KI<l|2$<6%s!<qn#F<>;$,
.=pack'N*',"@{[unpack'C*',$_]
}"for split/</;$_=$,,y[A-Z a-z]
         {}cd;print lc
[download]