Document :my and :our within regex blocks

[lefth]

:my and :our usage within regexes is not documented. For :my, something like this would be nice:

:my $foo = 0 is needed to declare a variable that has scope throughout and beyond the regex body, unlike variables declared in blocks. For example, the following trivial example shows a counter used for debugging:

$paragraph ~~ rx| :my $counter = 0; ( \V* { ++$counter } ) *%% \n |; say "Matched $counter lines";

If that's too verbose, a sentence or two could be added to the example that uses :my (but doesn't explain it).