k, did some testing and this is the winner:
code:
function arraycomp($1, $2, optional $m)
    dim $,$n
    for each $ in $2
        if (ascan($1,$)>-1&$m)|ascan($1,$)+$m<0 $n=$n+chr(1)+$ endif
    next
    $arraycomp = split(substr($n,2),chr(1))
endfunction
as you see, you also did not dim the $n...
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