For this kind of purposes, I use Getopt::Mixed.

#!/usr/bin/perl

use strict;

use Getopt::Mixed;

use vars qw|$opt_u $opt_x $opt_m|;
# Note that you have to use globals...

Getopt::Mixed::getOptions( qq|u=s x:i m:i| );
# Option u wants (mandatory) a string
# Option x accepts (not mandatory) an integer
# Option m too...

die "Hey man, you have to provide an username!\n" unless $opt_u ;
print "Option 'u' is $opt_u\n";
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Now your script will accept options from the command line, storing them in globals and complaining if you use options without their mandatory argument (i.e., you can't use a bare -u on the command line).

What makes Getopt::Mixed interesting is the possibility to specify longer synonyms for options. So, you can change a line of the script in this way:

Getopt::Mixed::getOptions( qq|u=s username>u x:i m:i| );
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username is a synonym for u, so that you can call your script from commandline is these two ways with the same results:

# getopt.pl -u larsen
Option 'u' is larsen

# getopt.pl --username larsen
Option 'u' is larsen

Update: Added an error message in case the user does not provide -u option