# not tested of course
my @message;
my $io = io('mail_file')->backwards->chomp;

while (my $line = $io->getline) {
  unshift @message, $line;
  last if($line =~ m/$message_start_pattern/); 
}
# @message now contains all lines of the 
# last message in correct order
for(@message){
   last if($_ eq "Content-Type: text/html;");
   print "$_\n";
}