I should have tested my code, I got confused and thought @- held the submatches themselves, not the indexes. So I actually meant $res{$&} = [ $1, $2, $3]; but got lazy :). And $res{$1} = [ $2, $3, $4 ] works without $& with the extra parentheses.

Your proposition has the benefit of not requiring to know the inner regex and its number of captures :)