C:\>type getopts.pl

use Getopt::Std;
our($opt_p);
getopts('p');
print "Using the getopts() method \$opt_p is ";
print defined $opt_p ? "'$opt_p'" : "undefined";

C:\>perl getopts.pl
Using the getopts() method $opt_p is undefined

C:\>perl getopts.pl -p
Using the getopts() method $opt_p is '1'

C:\>perl getopts.pl -p123
Unknown option: 1
Unknown option: 2
Unknown option: 3
Using the getopts() method $opt_p is '1'
C:\>