ff operator RHS always evaluates

[fecundf]

The Problem

$start-expr ff $end-expr always evaluates $end-expr, giving surprising side-effects.

I expect that the left-hand side, the $start-expr, must be True before evaluating the right-hand side, the $end-expr.

The issue as I see it is that the $end-expr always runs, even before the $start-expr toggles the flip-fop on.

Steps to Reproduce, Sample code:

say 'ff side effect=', gather { False ff .take for 1..5 };
say 'fff side effect=', gather { False fff .take for 1..5 };

Expected Behavior

ff side effect=()
fff side effect=()

Actual Behavior

ff side effect=(1 2 3 4 5)
fff side effect=()

Environment

• Operating system: OSX
  Tried this in two versions of Raku

1. This is Rakudo version 2019.11 built on MoarVM version 2019.11 implementing Perl 6.d.
2. This is Rakudo version 2020.07 built on MoarVM version 2020.07 implementing Raku 6.d.