$ perl -E 'say grep {++$i %2} <a b c d e f g>'
aceg
$ perl -E 'say grep {$i++ %2} <a b c d e f g>'
bdf

##</code><code>##

$ perl6 -e 'my @a = "a".."g"; say @a[0, *+2 ... +@a]'
aceg

##</code><code>##

@a[0, *+2 ... *]

##</code><code>##

say <a b c d e f g>.pairs.grep({.key !% 2})>>.value