From perldoc -f split:

If the PATTERN contains parentheses, additional list elements
are created from each matching substring in the delimiter.

   split(/([,-])/, "1-10,20", 3);

produces the list value

   (1, '-', 10, ',', 20)
[download]

Try using the non-capturing parentheses(?:)

update: Boy you gotta type fast around here!

update: changes from 'pre' to 'code', cause square brackets were being misinterpreted