You can also use combinations eg ctrlalt. The order of these matters as you have to put a combined mod ahead of the simple
Eg
/cast [mod:alt] spell1
/cast [mod:ctrlalt] spell2
Spell2 will never get cast as the line above it was found first. It needs to be laid out as the following instead.
/cast [mod:ctrlalt] spell2
/cast [mod:alt] spell1