It is expected that parsing errors can result in 'free' ⍺,⍵ variables in the workspace (outside of any lambda), and that they do not show up in )vars and cannot be deleted short of a )clear?
In a new, clear GNU APL session: {(⊂⍺){⍺[⍵;]}¨⍳≢⍵}⍨(3 4⍴⍳12) 1 2 3 4 5 6 7 8 9 10 11 12 ⍺ VALUE ERROR ⍺ ^ ⍵ VALUE ERROR ⍵ ^ ⍝⍝ As expected... {⍺{⍺[⍵;]}¨⍳≢⍵}⍨(3 4⍴⍳12) RANK ERROR λ1[1] λ←⍺ λ1¨⍳≢⍵ ^ ^ ⍺ 1 2 3 4 5 6 7 8 9 10 11 12 ⍵ 1 2 3 4 5 6 7 8 9 10 11 12 )erase '⍵' NOT ERASED: '⍵' )erase '⍺' NOT ERASED: '⍺' ⎕ex '⍺' 0 ⍺ 1 2 3 4 5 6 7 8 9 10 11 12 )vars )clear CLEAR WS ⍺ VALUE ERROR ⍺ ^