Perl Programs

While almost any language can be used for CGI, Perl is the one most widely used. It has the following advantages:

The use of here documents which greatly ease the problem of writing HTML and.or JavaScript programs from within the CGI program. Often the main purpose of a CGI program is to create HTML and/or JavaScript code which is sent back to the client for subsequent execution there. This happens so frequently that any formatting tools which reduce this problem are very important.
Access to server environmental variables, files, and processes: Perl lets you access many environmental variables, through the $ENV{} array, such as the PATH, HOME, or SHELL. You can invoke any Unix system command or user program through the "system()" routine, or within "backticks", such as `user/ucb/finger`, or through pipes which are treated like files, and can read/write or get information about files.
Perl contains very powerful string matching and substituting expressions (called "regular expressions") which are ideal for scanning files to locate or change information. For example,
```
/at(.)d*(c+)/
```
locates any string that starts with "at" followed by any single character followed by 0 or more "d's", followed by one or more "c's". It also stores whatever character it found after "at" in a variable named "$1", and the string of 1 or more "c's" is stored in $2.