Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

Here's an algorithm from the Camel Book:

    srand;
    rand($.) < 1 && ($line = $_) while <>;

This has a significant advantage in space over reading the whole file in. A simple proof by induction is available upon request if you doubt its correctness.