He meant 
my @dirs = grep { /\w/ && -d "$dir/$_" } readdir($dh);

[download]
which should probably be 
my @dirs = grep { !/^\.\.?\z/ && -d "$dir/$_" } readdir($dh);

[download]

In reply to Re^3: Recursive sub efficiency by ikegami
in thread Recursive sub efficiency by skywalker

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