Hi Jürgen,
I'm not sure if this is a significant enough change to add as a new file in GNU APL, but this change augments the Dyalog keyboard layout to have alt+tab "work". This behaviour is disabled on my computer (Debian) when I enable that layout:
address@hidden:~/aplstuff$ diff apl.tab.xmodmap trunk/support-files/Dyalog-Keyboard/apl.xmodmap
57c57
< keycode 64 = Alt_L Meta_L
---
> keycode 64 = Mode_switch Meta_L
101c101
< keycode 108 = Alt_L Meta_L
---
> keycode 108 = Mode_switch Meta_L
File is attached
-Alex
apl.tab.xmodmap