in reply to
-> Is Optional ?
Yes. See the docs in perlreftut which says :-
In between two subscripts, the arrow is optional.
Priority 1, Priority 2, Priority 3
Priority 1, Priority 0, Priority -1
Urgent, important, favour
Data loss, bug, enhancement
Out of scope, out of budget, out of line
Family, friends, work
Impossible, inconceivable, implemented
Results (60 votes),