> so it will be stupid to pass 0

It's better not to expect software (or users) to be smart, even in a draft.°

> to my SSCE

why does an SSCCE even need defaults?

> // is available iirc since 5.14

defined or $#ARGV are older.*

FWIW: I don't support KGB's tone here, I'm just saying playing safe is easy here.

°) I have similar discussion regularly with my clients:

• "Who would ever do this?"
• "Sigh ... Wait and see!"

Half a year later

• "Who could have ever expected this?"
• "Sigh ... No one! (and thanks for the salary)"

updates

*) BTW 5.10.0 https://perldoc.pl/perl5100delta#Defined-or-operator