my %hash;
for (@filenames) {
   chomp;
   push @{$hash{$3}}, $_  if ($_ =~ /(.+)\/(.+)\/(.+)\/.+/);
}

for (keys %hash) {
   print "#".uc($_)."\n" ;
   print $_."\n" for (@{$hash{$_}});
   print "#END ".uc($_)."\n" ;
}