Perl Modules

The properties of Perl Modules:

  • Modules either come with Perl or can be downloaded from CSPAN
  • Modules can also be custom written
  • Libraries also exist, but the difference is:

Libraries mostly contain similar subroutines

Modules is like a “smart library” – offers collection of subroutines that act as if they were build in functions

Modules are more commonly used in Perl than Libraries

  • Some basic modules that already come with Perl are discussed below.
  • File::Basename Module

Include the following at the top of file

  • use File::Basename
  • This works well in UNIX but need to be cautious when using in Windows
my $name = "/usr/local/bin/perl";
 my $dirname = dirname $name; # set as bin
 my $basename = basename $name; # set as perl
  • File::Spec Module

Used for manipulating file names, directories, and other stored file system information

Again this can work well in UNIX but needs to be cautioned on other OS

my $new_name = File::Spec -> catfile($dirname, $basename);
  • Some other common modules:

Cwd Module

  • This module tells you the current working directory



  • Replaces the do / die



  • Be able to send email through an SMTP server


  • Contains POSIX functions





  • To overload existing functions (addition, subtraction, etc)

Common Gateway Interface

  • Comes with Perl
  • Easy way to form parameters and generate HTML responses

For webpage creation

Has many functions to print HTML


 use CGI qw(:all);
 print header("text/plain"), # Creates the HTML header
 start_html("This is the page title"), # printing start of HTML
 h1("Header Description Here"); # h1 function makes an H1 header

my $list_items;
 foreach my $param ( param() ) { # function to get param values
 $list_items .= li( "$param: " . param($param) ); # concating a list of param values
 print ul($list_items); # printing the param list values as a list to HTML
 print end_HTML(); # ending the HTML document
  • Databases and DBI

Doesn’t come with Perl but is the most popular module used

Uses same interface to connect to almost any database, from Oracle to whatever database (ODBC) driver exists

Download Perl DBI (module name)

Check http://dbi/ for more information

  • Pragma

These are special modules that come with Perl for the internal compiler

  • For example: use strict # this is a pragma

Other examples are:

  • Constant
  • Tells the compiler that a given identifier has a constant value
  • Diagnostics
  • Compiler refers to the perldiag manpage to give more analysis on error messages
  • Lib
  • Tells Perl that the given directory is the first place to look for modules
  • Vars
  • Warnings
  • Available in Perl Version 5.6 and up only