I'd start by examining how existing CPAN modules parse natural language. The modules in the Lingua::* namespace might provide some useful starting points.

Also, off the top of my head: Time::Human kinda does what you're talking about, but in the other direction. Date::Manip accepts a wide range of "natural language" input for dates, so that might also be a great start for you.

Update: From the Date::Manip POD:

  $date = ParseDate("today");
  $date = ParseDate("1st thursday in June 1992");
  $date = ParseDate("05/10/93");
  $date = ParseDate("12:30 Dec 12th 1880");
  $date = ParseDate("8:00pm december tenth");
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The range of input accepted by this module might eliminate a lot of work for you!

blokhead