Bizarre interaction between explict for loop variables and iterators

wat.p6

sub wat ($n) {
    ($n .. 1).map: -> $m { say "uno: $m" }
    ($n .. 1).map: -> $m { say "dos: $m" }
}

for ^2 -> $m { say "|$m|"; wat($m) } # explicit for loop variable
say '';
for ^2       { say "|$_|"; wat($_) } # implicit for loop variable