use v6;
################################
# Recursive solution by iblech #
################################
my @loops = ([1..3], ['a'..'e'], ['foo', 'bar']);
sub outer(*@vals) {
my &helper = -> @prev, @rest {
if @rest {
# We've still got a rest to interate over.
# We add all items of @rest[0] to the new @prev
# in our sub-helper, and use @rest[1...] as new
# rest, i.e. all elements of @rest except the
# first one.
helper [ *@prev, $_ ], @rest[1...] for @rest[0];
}
else {
# We don't have to recurse further, so we
# simply "return" @prev.
take @prev;
}
};
# @prev: Empty array
# @rest: @vals
gather { helper([], @vals) };
}
my @a = outer @loops;
say join "\n", @a;