# Assume that the header is all the first block of commented
# lines and that the first non-comment line ends the 
# header block
while (<OLDFILE>) {
  last unless is_comment($filetype, $_);
}

# Print new header to new file
print NEWFILE new_header($filetype);

# Print the rest of the file
while (<OLDFILE>) {
  print NEWFILE $_;
}