Backreferences in regexes match, but do not capture

Question

This program

say "zipi zape" ~~ /(\w)\w» \s+ \w+({$0})/;

returns

｢pi zape｣
 0 => ｢p｣
 1 => ｢｣

which I interpret as the backreference to the first match being matched to a zero-width match? Maybe because it's matched to $0, which is itemized to '' outside the regex? How could I use these backreferences, and capture at the same time the match? Note: this related to this documentation issue, which requires clarification of the use of backreferences.

Answer 1

According to the documentation:

If you need to refer to a capture from within another capture, store it in a variable first

So you could use:

say "zipi zape" ~~ /(\w){} :my $c = $0; \w » \s+ \w+($c)/;

Output:

｢pi zap｣
 0 => ｢p｣
 1 => ｢p｣