Check multiple variables in DSP

How can I check more than one variables in DSP if they are empty. For example, can I use
%ifvar variabl1 -isnull || ifvar variable2 -isnull || ifvar variable3 -isnull%
do something
do not do anything

I am also not sure that if this is the correct way to compare more than one variables, then should I have to put every %endif% for each of the variable at the end?