If you're sick and tired of backslashing double quote signs, and you want to know why you can't print "firstname.lastname@example.org" without Perl yelling at you, this article will clear things up for you. We'll straighten out the uses of Perl's varying quoting operators, and learn about interpolation.
While many people know what files and filehandles are in Perl, there are many times that people forget exactly how they should be used. Too often people open files incorrectly, causing data to be lost, or they expect a file to exist, when it really doesn't, and their program lacks the proper error reporting to alert them. Let's fix these problems up first.
Environment variables are pieces of information gathered by the Common Gateway Interface (CGI). This
data is available to all cgi programs, allowing you to know not only some information specific to your
web server, but also giving you insight on who is visiting your site, with what kind of browser, how
they're accessing your program among other useful information.