Know thy FAQs :)
This specific question can be found in
perlfaq7 under "
How do I create a switch or case statement". It even has 4 examples.
I recommend reading all of the FAQs. You can just scan through the headlines and forget the answers - so when you need an answer, you'll know where to find it.
perldoc -q can be very handy. In this case,
perldoc -q case or
perldoc -q switch would have found the answer for you.
2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$