I tried to put use 5.10.0 into this script and found a problem ...

> sub when (&$){                          # guard

when can't be easily used, since it's reserved for given/when

I tried to find another short (max 5 letters) synonym for if , but that's pretty difficult.

my best guesses are

• cond(ition)
• prov(ided)
• case
• guard

Synonym for while is easier, I'd choose whilst , this pair corresponds well with 'for/from'.

any better idea for if ?