Split on last occurance

I want to call a script like this:

./somescript some-thing[who].knows.what.ending

Inside the script it needs to split at last .(period)
so I can:

a=some-thing[who].knows.what
b=ending

I know I can do it in perl but im still learing awk and sed.

Thanks

Use parameter expansion.

a=${1%.*}
b=${1##*.}

Do you really want to use awk or sed?

Not if I dont have too...

Is there a cheat sheet somewhere for these?

Works great thanks...

How can I use parameter expansion?