Why don't you just concatenate "$hifolder/$lowfolder"? That is unique and gives you the absolute path that you would wind up using to delete the directory anyway. You probably need to prepend $hipath to the $highfolder name perhaps in the loop that iterates over the $highfolders".

my @FullDirPaths = map{"$hipath/$highfolder/$_"}@LowFolders;

You might want to look at Date::Time module for comparing dates. Or you could make a little YYYYMM "date math" routine yourself, but I suspect that using the module will be easier.

Don't know if this is a typo or not, but don't put a ";" after the "->" ie have "->new();"

Update: Don't know where my brain is this morning...Actually I don't think that you need to save the @FullDirPaths like above at all. At this point in the code you have all 3 parts of the full path: "$hipath/$highfolder/$lowfolder". Just decide right there whether or not you should delete this particular $lowfolder or not! No need to save the names to process later. You can use a simple regex to separate out the month and year from the filename like shown below...

my @dates = ( '1010', '1007');

foreach my $date (@dates)
{
   my ($year,$mon) = $date =~ m/\d\d/g;
   print "year = $year month= $mon\n";
}
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