$ perle '
    open my $fh, "<", "pm_1208018_test_dir/pm_1208018_test_file";
    opendir(my $dh, "pm_1208018_test_dir");
    opendir(my $eh, "pm_1208018_test_dir_empty");
    opendir(my $ch, "pm_1208018_test_dir_closed");
    closedir $ch;
    my $nh = "42";
    my $uh;
    my %h = (fh => $fh, dh => $dh, nh => $nh, eh => $eh, uh => $uh, ch => $ch);
    for (keys %h) {
        use warnings FATAL => "io";
        eval {
            my $x = telldir $h{$_}; say "$_ is a dirhandle"; 1
        } or say "$_ is not a dirhandle" 
    }
'
fh is not a dirhandle   # fh = filehandle
nh is not a dirhandle   # nh = not a handle (just the number 42)
eh is a dirhandle       # eh = dirhandle to "pm_1208018_test_dir_empty"
dh is a dirhandle       # dh = dirhandle to "pm_1208018_test_dir"
ch is not a dirhandle   # ch = closed handle
uh is not a dirhandle   # uh = undefined handle (declared but uninitialised)