Thanks for the suggestion! I did as you suggested:

use Fcntl ':mode';

my $mode = ...;
if (S_ISDIR($mode)) {
  # directory
  ...
}
[download]

But still no joy. It simply doesn't enter the "if" block, even though I'm doing a stat on a directory. I suspect it's got something to do with the fact that the files (and dirs) are on a remote host. Anyway, reading the docs on the builtin stat has shown me how to get the permissions, i.e.

my $ssh2 = Net::SSH2->new();
my $sftp = $ssh2->sftp();

my %fstat = $sftp->stat("${testdir}");

my $perm = $fstat{"mode"} & 07777;
[download]

But is there no way to get the file type in the same way, i.e. using an & operator on the mode?

Many thanks..