For what you want you need a couple of Getopt::Long options.

[05:53][nick:~/monks]$ cat 1134359.pl
#! perl -w
use strict;

use Getopt::Long;
Getopt::Long::Configure( "bundling", "ignorecase_always" );

my $myOpt=0;

GetOptions('S=i'=> \$myOpt);
print"S: $myOpt\n";

__END__

[05:53][nick:~/monks]$ perl 1134359.pl -S 6
S: 6
[05:53][nick:~/monks]$ perl 1134359.pl -s 6
S: 6
[05:53][nick:~/monks]$ perl 1134359.pl -S6
S: 6
[05:53][nick:~/monks]$ perl 1134359.pl -s6
S: 6
[download]

The docs have much more to say on bundling options. Like what if you have an option -foo as well as -f and -o, the latter of which takes a required value when the others don't. What happens if the user does script.pl -foo?

Maybe take note of the following line from the docs: "It goes without saying that bundling can be quite confusing." :-)

[05:53][nick:~/monks]$ perl 1134359.pl -zois6nks
Unknown option: z
Unknown option: o
Unknown option: i
Unknown option: n
Unknown option: k
Option s requires an argument
S: 6
[download]

Yep, still '6' ...