You also have to test that what you're getting are really dirs.

No. opendir already does that. Checking it explicitly is redundant at best, and adds a race condition at worse.

Isolate your directory path value

That's a great idea since it allows you to print it in the error message, something you failed to do. This would have been extremely useful to the OP. 

$ perl -e'
    my ($dir_qn) = @ARGV;
    opendir(my $dh, $dir_qn)
        or die "Can'\''t open dir $dir_qn: $!\n";
' somefile
Can't open dir somefile: Not a directory

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In reply to Re^2: Quickest way to get a list of all folders in a directory by ikegami
in thread Quickest way to get a list of all folders in a directory by Anonymous Monk

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