I take "valid identifier" to mean something which is syntactically valid as an identifier, rather than something that is in the finite set of identifiers which C<form> actually uses.
Correct.
Although, as Larry pointed out, given the compile-time nature of option keys, there's no reason subroutine arguments labelled using the option syntax couldn't be checked for validity against the subroutine's named parameters as compile-time too.
Using the C<< => >> it's possible to construct pairs in which the key is not a valid identifier:
'Hello there' => 'contains a space', '2b' => 'starts with a digit', '%^&@";' => 'only punctuation characters',
None of those keys could result from using the C<:> option constructor.
Exactly.
Damian
