altkey() down, up & halfway down

[Richmond]

Has anybody any bright ideas why this doesn't work:

on mouseUp
    if altkey() is down then
       put "ALT key is down" into fld "fOUTPUT"
    end if
end mouseUp

or this:

on mouseUp
    if the altkey is down then
       put "ALT key is down" into fld "fOUTPUT"
    end if
end mouseUp

on Linux?

'Tisn't funny, m'dears!

Richmond.