Trace should show that it executed each line even if that line doesn't produce a value. i.e.
GNU APL:
∇test[⎕]∇
∇
[0] test
[1] ⍝ a comment
[2] test2
[3] x←4
∇
∇test2[⎕]∇
∇
[0] test2
∇
T∆test←⍳3
test
test[3] 4
IBM APL 2:
∇TEST[⎕]∇
∇
[0] TEST
[1] ⍝ A COMMENT
[2] TEST2
[3] X←4
∇
∇TEST2[⎕]∇
∇
[0] TEST2
∇
T∆TEST←⍳3
TEST
TEST[1]
TEST[2]
TEST[3] 4
Thanks.
Blake