package MyApp::URLFetcher::NetFTP;
use base qw/MyApp::URLFetcher/;

use Net::FTP;

sub get_url_to_str {
    my $self = shift;
    my $url = shift;

    # I don't know Net::FTP
    # either way, our interface is a bit harder to pull off 
    # with Net::FTP
    # but this complexity will be in the software anyway
    # it's better to hide it here
    my $f = Net::FTP->new; # ...
    # ...
    $f->get("...");
}