`.toggle` is hard to understand and should be DEPRECATED

[lizmat]

See discussion at rakudo/rakudo#2089 and the issue rakudo/rakudo#2088.

[librasteve]

read some of the references, I agree that toggle is too hard and that the main practical concern is the effect of varying data on the consumption of the test chain

I can see in a Method chain, or a Supply / Tap context that it is useful to have functions that:
a. filter values (eg to cap, collar real world data perhaps)
b. turn on / off the feed depending on value gates within the data (eg inspect the contents of "packets")

(a) can be done with grep: -5 < * <= 5
(b) can be done with a modification to toggle

therefore I propose the following modification / simplification of toggle:

toggle should only take one test which should be repeatedly applied to each element in the list (ie the notion of stepping along the args should be scrapped)

(1,2,3,0,3,3,3,0,1,2,0,2,2,0).toggle( *==0, :off ) => 3,3,3,2,2

Callable & Matcher both seem good for this use case

Apologies if there is another good way to do this in raku that I do not know

Another adverb pair :include, :exclude (default include) is needed to gate whether the tested element is passed through

EDIT: based on @lizmat example below, I will withdraw this idea

[lizmat]

% raku -e 'my $on; say (1,2,3,0,3,3,3,0,1,2,0,2,2,0).map({ if $_ == 0 { $on = !$on; Empty } elsif $on { $_ } })'
(3 3 3 2 2)

[CIAvash]

say (1,2,3,0,3,3,3,0,1,2,0,2,2,0).grep({ 0 ^fff^ 0 })
=output (3 3 3 2 2)

[2colours]

I tend to agree that .toggle never really caught on and the abstraction it provides is neither efficient nor particularly useful. However, I also agree with @FCO who went ahead and created this module that "takewhile", "dropwhile" kind of functionality is useful and currently the only reasonable functional (non-gather-take) core way to achieve it seems to be .toggle. This is something to consider for the future.