use IO::File;
use Fcntl qw(:seek);

my $fh = IO::File->new_tmpfile 
  or die "Couldn't create tempfile: $!\n";

print $fh <<"END";
The contents of the file.
END

seek $fh, 0, SEEK_SET 
  or die "Couldn't rewind temp file: $!\n";

$ftp->put($fh, "ftptest");

close $fh;
# tempfile should be gone now.