Well, "APRIL, MAY, JUNE" is just a list of three strings. Perl is iterating across each element in that list and doing the stuff inside the for loop exactly three times, once for each string.

Elsewhere in the program I assume you did something like open APRIL, "<200204";. If that's the case, you need to use the special angle bracket operator to iterate through each record in a file, like while(<APRIL>) {do stuff}. Note also that while you are looping through each file you still need to perform the split on each record in order to find the name that's on a given record.