my %set01 = ();
$set01{$_} = 1 foreach (glob("*.*");  # identify each file in directory

..... # code that creates secondary files

#    my @new_files = ();                             # keep a list of new files if you want
my @set02 = glob("*.*");
foreach (@set02){
#    push @new_files, $_ unless(exists($set01{$_}))

    unlink $_ unless(exists($set01{$_}));  # delete files that weren't aren't in original set 

}
print "original files\n",sort keys %set01,"\nnew files\n",sort @set02,"\n";