in reply to Infinity and Inf?

But I would be interested to know the canonical/intended way to use those constants, before messing around with internals!

There is, if you're willing to use v6;:

$ perl6 -e 'for 1..Inf { .say; last if $_ == 5 }' 1 2 3 4 5
Perl 6 - links to (nearly) everything that is Perl 6.