my %opt = @_;

##</code><code>##

    ( -d "$opt{ dir }/$_" )   # is a directory

##</code><code>##

      && !/^\./               # is also not hidden/special

##</code><code>##

      && /(\d{4}_\d{2}_\d{2}_\d{2})/
                              # contains date/hour

##</code><code>##

      && ($opt{ now } gt $1 ) # that is in the past