turnstep's suggestion is excelent. There are 2 other modules you may want to check out:

1. Text::Soundex - good for determining is words sound-alike
2. Text::Metaphone - better algorithm that Text::Soundex and good for phrases

You didn't say in your question if the "similar data" you're trying to match is strings or not. If it is numeric a simple +- %5 type algorithm would work well for determining similarity. For comparing strings one of the simplest algorithms you can use is ignoring case ("ANOTHER MAN DOWN" and "Antoher Man Down" are considered the same thing). Its not very powerful but it is very easy to do.

Different algorithms may work better depending on exactly what piece(s) of data you want to de-duplicate on. If you're deduplicating on multiple fields some sort of hybrid de-duplication algorithm may be best. Here's an example deduplication scheme I cooked up for a database of people, where they live, and what their income is:

(String::Approx of LAST_NAME the same) and (INCOME within %5) and (STATE the same)

In my experience coming up with a de-duplication scheme for user-entered data is easy. Coming up with a good one is hard and may take weeks or months of tuning.