How to compare text?

[A]

Hello,
How can I compare of one  parragraph of text with another
paragraph?Each paragraph can have about 100 words.
For example I have the first paragraph

I want to be very good at Python programming. Better than in Perl.

THe second paragraph might look loke this:

She works all day long to master Perl.

All that I need is to find out if any of word from the second is in the 
first paragraph. For the example above I should find out word

Perl


What is the best and quickest way?
Thank you for help.
Ladislav