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
⍺
^