use File::Find;

use Data::Dumper;
my @directories = ("/u/files", "/tmp");


my @readfiles;
File::Find::find({
                preprocess => sub {
                sort {
                  # Files sort before dirs
                  (-f $a ? (-f $b ? $a cmp $b : -1 ) : (-f $b ? 1 : $a cmp $b))
                   } @_
                },
                wanted => sub {push @readfiles, "$File::Find::dir/$_" if (-f); } ,
                postprocess => sub { rmdir $File::Find::dir },

                }, @directories);


print Dumper \@readfiles;