Okay... so did you try following the directions about usage? It is telling you that you need to give it some input. Read the program!

=head1 SYNOPSIS

nohup ./renamer image /home/httpd/htdocs /home/me/images jpg &

=head1 DESCRIPTION

#The above instructs renamer to look for files called image.jpg in /home/httpd/htdocs.
#It checks once per minute for such a file to appear. If it sees a
#readable file called /home/httpd/htdocs.jpg it moves it to
#/home/httpd/htdocs/image.200302251530.jpg where the number is a
#time stamp with year (four digits), month, day of the month, hour (in
#24 mode), and minute.