[*]

See also “a better way to accomplish what I (OP) wanted”.

See also “Some possible solutions” answer to “How can I completely flatten a Raku list (of lists (of lists) … )” question.

Add a subscript

my \perm = <a b c>.combinations(2)».permutations;
say perm;       # (((a b) (b a)) ((a c) (c a)) ((b c) (c b)))
say perm[*];    # (((a b) (b a)) ((a c) (c a)) ((b c) (c b)))
say perm[*;*];  # ((a b) (b a) (a c) (c a) (b c) (c b))
say perm[*;*;*] # (a b b a a c c a b c c b)

Notes

I used a non-sigil’d variable because I think it’s a bit clearer what’s going on for those who don’t know Raku.

I didn’t append the subscript to the original expression but I could have:

my \perm = <a b c>.combinations(2)».permutations[*;*];
say perm;       # ((a b) (b a) (a c) (c a) (b c) (c b))