First, surround any data or code with CODE tags. If I understand you correctly, your data looks something like this:

Header Line One
***-*** 0 0 ***-MBO 0 0 2TO-T/V 0 0 2TO-T/O 0 0 POC-CNU 1285 0 POC-A/M
+ 0 15567
Header Line Two
***-*** 0 0 ***-MBO 0 0 2TO-T/V 0 0 2TO-T/O 0 0 POC-CNU 1285 0 POC-A/M
+ 0 15567
[download]

Although you do not specify, I'll also assume that the header lines alternate between 'one' and 'two', and you just want to make sure that these don't repeat (that is, they continue to alternate).

Here's what I'd try:

#!/usr/bin/perl -w
use strict;

# variable to hold the previous header 
my($header);

foreach (<>) {
  if (/^Header Line (\S+)$/) {
    die "Error - header repeated in line $.\n" if ($header && $header 
+eq $1);
    $header = $1;
    next;
  }
  if (/^[\w\*\/]{3}-[\w\*\/]{3}/) {
    # do whatever processing on the line
    print "Got a matching line...\n";
  }
}
[download]

Hope that helps,
Shendal

Update: Darn. Looks like I got your data wrong - or zzamboni did (grin). All the more reason to use CODE tags.