It is my understanding that debian doesn't use rpm (it's only for Red Hat/Fedora and their ilk). See the note here http://packages.debian.org/stable/admin/rpm and here http://www.debian.org/doc/manuals/distribute-deb/distribute-deb.html I'm sure there is a .deb package for vsftp so this is what I'd do if I were you ...

#! /usr/bin/perl

use strict;
use warnings;

system("apt-get install vsftp"); # Note I don't actually know if this 
+is the correct syntax for apt-get as I usually use the evil RHEL
[download]

Personally I don't understand why you want perl to do the install for you. Could you provide some more info on what you're trying to do? It would be alot easier just to type the command on the CLI.