You're right. Sorry, I was a little quick to correct the "," to "=>", but I think the comma works fine as you pointed out. I'm so used to using "=>" that at first glance I thought using the comma was illegal. The "as long as you know that the list has an even number of elements..." part is enough for me to use the 2nd version ("=>") since I know the 2nd one works all the time :-) In fact all the perl documentation on hashes shows the "=>" operator.
As I think you'll agree, in this code:
my %hash = ('a', 'b', 'c', 'd');
it is not clear that 'a' is the key referring to value 'b'.
