If you could use some other module, File::Slurp provides a read_dir function which can be used as follows.

read_dir returns a list of directory contents.

grep -d selects only directories (filtering out files).

use File::Slurp;

my @dirs = grep { -d "$dir/$_" } read_dir($dir);
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To include the . and .. special directories, add the keep_dot_dot option:

my @dirs = grep { -d "$dir/$_" } read_dir($dir, keep_dot_dot=>1);
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