$ftp->cwd($i2) or die "change directory $i2: ".$ftp->message." / ".$ftp->code;
my @nfiles = $ftp->dir;
if(grep {$_ eq $i3} @nfiles){
die "make $i3: already exists";
} else {
$ftp->mkdir($i3) or die "make directory ".$ftp->code;
}