I'm writing a perl script that takes a "duration" option, and I'd like to be able to specify this duration in a fairly flexible manner, as opposed to only taking a single unit (e.g. number of seconds). The UNIX at command implements this kind of behavior, by allowing specifications such as "now + 3 hours + 2 days". For my program, the "now" part is implied, so I just want to parse the stuff after the plus sign. (Note: the at command also parses exact date specifications, but I only want to parse durations.)

Is there a perl module for parsing duration specifications like this? I don't need the exact syntax accepted by at, just any reasonable syntax for specifying time durations.

Edit: Basically, I want something like DateTime::Format::Flexible for durations instead of dates.