[IBM APL2] )CLEAR CLEAR WS ⎕IO←0 M←¯12+⍳25 )OUT OUT
[GNU APL] )IN OUT ERROR: inverse 2 ⎕TF failed for 'M←¯12-⎕IO-⍳25 I'm assuming the error here is on the GNU APL side of the transaction, as APL2 has been around for a while, and people would have complained. ;