in reply to Regex pattern to find directories only with digits

with this format "20130411". Not "2013.kjh" or "NN.201304", or "2013mmkk04".

You might need to refine your definition of 'this format'. Must it be a valid date ? Can it be in the future ? Can it be anywhere in the past ? Could it be less than 8 digits ? ... Etc. If you'd want _precisely_ 8 digits and wouldn't care about validness of the date,

m/^[\d]{8}$/ might be the regex you want,