How to search using partial words?
That's because Craft doesn't do fuzzy searching by default.  You'd need to use the wildcard 'Peru*' to match 'Peruvian'.  You can see the full list of supported search syntaxes here: http://buildwithcraft.com/docs/searching

Related, you might want to vote for this feature request: http://feedback.buildwithcraft.com/forums/285221-feature-requests/suggestions/8459443-add-option-to-enable-fuzzy-search-as-default

Update:
As of Craft 2.5, you can enable fuzzy searching by default.