well this is untested code, but maybe something like this:
compare_sites("newsite1.txt", "newsite2.txt")
if day eq "monday..." # psuedo code
compare_sites("newsite2.txt", "newsite1.txt")
if day eq "tuesday..." # psuedo code
sub compare_sites {
my $file1 = shift;
my $file2 = shift;
open IN1, $file1;
while(<IN1>) {
chomp;
$newsite1{$_}++;
} # while
close IN1;
open IN2, $file2;
while(<IN2>) {
chomp;
print "$_ is a new site\n"
if not defined($newsite1{$_});
} # while
close IN2;
} # compare_sites
Hopefully memory isn't a problem... but otherwise this shouldn't be too bad a solutions
UPDATE:
changed the code to a function as per tye's suggestion (and so he doesn't think I'm trying to make him look like an idiot I added this comment)... and added psuedo code for calling the function based on dates... :P
UPDATE:
changed the does not exist line to print the site name and not a number... plus it identifies that it is a new site...