my %cksums;

for my $file ( grep { $_->has_content } @files ) # only do non-empty files
{
   next if $file->uname eq 'root';  # let's leave these alone

   if ( $file->name =~ /\.[ch]$/ ) {
      # do things with source code files here...
   }
   elsif ( exists( $cksums{ $file->cksum } )) {
      # file's content duplicates another file we've already seen...
   }
   else {
      $cksum{$file->cksum} = undef; # keep track of cksums
   }
}