ngspice has also loopcontrol so you can do things like:

.control

let run=1

dowhile run <= 40

if run > 1

reset

set appendwrite

end

save saout cal i(vvcc) en plus minus

tran 0.1n 900n uic

write autozero_comp.raw

let run = run + 1

end

.endc

This is how i managed to run a montecarlo sim...