When I used Genstat in the mid 1990s I could achieve the same sort of thing using syntax like:

2(1),4(2) = 1,1,2,2,2,2

there were other more flexible ways along the lines of:

2(1,3) = 1,1,3,3
(1,3)2 = 1,3,1,3
(1...3)= 1,2,3
2(1...3)=1,1,2,2,3,3
(3...1)2=3,2,1,3,2,1
2(0,2...6)=0,0,2,2,4,4,6,6

it may have been possible to have repetition factors at both ends, but I don't recall that.