[Bug-apl] Why do I hit this SYSTEM LIMIT?

[Peter Teeson]

      c←⍳9
     d←(((('c',('n',⊃⍕¨c),'←'),'⍳'),'0'),'  '),'◊'
SYSTEM LIMIT (prefix length)
      d←(((('c',('n',⊃⍕¨c),'←'),'⍳'),'0'),'  '),'◊'
                      ^                       ^
 but this is OK? 
    d←((('c',('n',⊃⍕¨c),'←'),'⍳'),'0'),'  '

I don't see prefix length in ⎕SYL.

I don't understand. Sorry but my coffee must not be working….

Peter