my $debug = ""; 

*Net::FTP::debug_print = sub { my ($cmd,$out,$txt) = @_; $debug .= $txt; }; 

my $ftp = Net::FTP->new("domain.tld", Debug => 1); 
$ftp->login( "user", "password" ); 
print $debug;
__END__
Net::FTP(2.75)
  Exporter(5.58)
  Net::Cmd(2.26)
  IO::Socket::INET(1.31)
    IO::Socket(1.31)
      IO::Handle(1.28)
220 (vsFTPd 2.0.5)
user user
331 Please specify the password.
PASS password
230 Login successful.