Sometimes, when you have, essentially, a WS full situation, GNU APL just dies instead of giving a WS FULL error.
x←⍳100000000
x[10000]←445
y←x
/home/blake/bin/apl: line 3: 7341 Done akt
7342 Killed | /usr/local/bin/apl "$@"
address@hidden ~ $ apl
x←⍳100000000
/home/blake/bin/apl: line 3: 7964 Done akt
7965 Killed | /usr/local/bin/apl "$@"
address@hidden ~ $ apl
x←⍳10000000
⍴x
10000000
y←x
x←⍳10000000
x←⍳100000000
WS FULL
x←⍳100000000
^ ^
)off
address@hidden ~ $ apl
x←⍳100000000
/home/blake/bin/apl: line 3: 7992 Done akt
7993 Killed | /usr/local/bin/apl "$@"