use Getopt::Std;
Getopt::Std::getopts( 'a:b:de' );

This call sets up five command-line switches: a, b, d, and e. 
The colons after a, b tell getopts that a, b require values.
d, and e are called Boolean switches. 
Boolean switches are either set or not.

For example, the following sets a Boolean switch:

command -d

The following sets a switch with a value:

command -a value

With the Getopt::Std module, the getopts routine sets variables starting with opt_ for each option that is set. For example, the -a switch corresponds to the $opt_a variable. Thus, you can use the following code to look for a -a switch: 

use Getopt::Std;

Getopt::Std::getopts( 'a' );

if ( defined( $opt_a ) ) {
    print "-a flag set to $opt_a\n";
}