my $n = (1..10)
    .grep({ $_ mod 2 != 0 })
    .map({ $_ ** 2 })
    .reduce: { $^a + $^b };

$n == 1 ** 2 + 3 ** 2 + 5 ** 2 + 7 ** 2 + 9 ** 2 or die "Wrong value";