It was possible to set the random seed by assigning to ⎕RL in v1.3, but this doesn't seem to work in v1.4.
______________________________________________________________________ v1.4 session ______________________________________________________________________ ⎕RL 16807 ⎕RL ← 17 ? 10 5 ⎕RL ← 17 ? 10 6 ⎕RL ← 17 ? 10 5 ⎕RL ← 17 ? 10 8 ______________________________________________________________________ ______________________________________________________________________ v1.3 session ______________________________________________________________________ ⎕RL 1 ⎕RL ← 17 ? 10 8 ⎕RL ← 17 ? 10 8 ⎕RL ← 17 ? 10 8 ______________________________________________________________________