more fun: cat, hcat, vcat
more fun: cat, hcat, vcat

A = matrix(fmpz, 2, 3, [1,2,3,4,5,6])
cat([1,2], A, A, A)
cat([1,2], [A[:, i] for i=1:3]...)
cat([1,2], [A[i, :] for i=1:2]...)
[A A A; A A A]
should all work.
I'm not claiming it's fast

thofma/Hecke.jl