MSG-HDR |UB

##</code><code>##

MSG-HDR
bla
|UB

##</code><code>##

my $orderfound = 0;

while (my $line = <>) {
   if ($line =~ /MSG-HDR/) {
      $orderfound = 1; 
      next;
   }
      
   if ($orderfound && $line =~ /\|UB/) {
      print "$line\n";
   } 

   $orderfound = 0;
}