If while (<STDIN>) does something you don't expect, the Perl documentation should be your first port of call. You can...

• google for perldoc while
• search for while at http://perldoc.perl.org
• Use perldoc perlsyn from the command line (unfortunately you need to know that while's described in perlsyn)
• If you're using ActivePerl on windows, Perl's documentation can be accessed via Start -> Programs -> ActivePerl -> Documentation.