sub fs ( Code $f, @s ) { @s.map: { .$f } }

sub f1 ( $n ) { $n *  2 }
sub f2 ( $n ) { $n ** 2 }

my &fsf1 := &fs.assuming(&f1);
my &fsf2 := &fs.assuming(&f2);

for [1..3], [2, 4 ... 8] X &fsf1, &fsf2 -> ($s, $f) {
    say $f.($s);
}