Perl CGI Programming

CGI Paradigms

• There is an object oriented and a procedural interface to the Perl CGI library. We will be exclusively using the Object Oriented interface.
• To use the CGI module, include the following line your Perl program:
  use CGI;
• You must also instantiate a Perl CGI object. For example, to create an object named "query", use:
  $query = new CGI;
• The actual syntax for supplying an argument to a CGI object method would be as follows (this example uses the header CGI method):
  print $query->header({-type=>'image/gif', -expires=>'+3d'});
• The arguments in the curly braces are HTML tag modifiers. The arguments not in the braces are the contents between the open and closing tags.
• For example, the following Perl CGI construct:
  

  print $query->h1({-align=>'center'}, 'Hello', 
  		 $query->em('World'), '(two)!');
  

  
  Generates
  

  <H1 ALIGN="center">Hello <EM>World</EM> (two)!</H1>
  

• Naturally, like the rest of Perl, these arguments can be scalars, arrays, or hashes. Like the rest of Perl, you never really know for sure when to pass which. Like the rest of Perl, if you go with your gut, it will probably almost always work out fine nonetheless.
• Examples on the upcoming pages will demonstrate the syntax involved for these different argument types.