To find programs that already do what you want, search for a 'concordance' generator. I have a few of these laying around since I assigned it as homework. None are production quality but I can post one if you would like.

In order to remove word endings, find the stem of each word. This is called 'stemming'.

There are modules for each of these on CPAN. Lingua::Stem and WordNet::QueryData, although the WordNet module is overkill for what you need.