I strongly recommend using the /x flag with your large regexen to make them more readable and maintainable. It can help code readability to put the regex into a variable too so the flow logic can be seen easily. Consider:

use strict;
use warnings;

my $regex = qr|
  Primary\s\(Reporting\)\s
  Cp\s*:\s*((?:(?!Set).)*)  # Now we can see what's happening
  Set\s*:\s*((?:(?!Car).)*) # but why are the look aheads needed?
  Car\s*:\s*((?:(?!Ref).)*)
  |six;

while (<DATA>) {
  next if $_ !~ $regex;
  print;
}
[download]

__DATA__
====================================================================
Record: 9851329   Version:  2   Timestamp: Sat Feb 11 22:39:43 2006
Primary (Reporting) Cp: 113  Set: 2 Car: 1  Ref: yes  Event:   9922
Missing P:  Keep: 1  Phase: 0x2fdf  Strength: 24
Secondary Sector Information:
====================================================================
Record: 9851330   Version:  2   Timestamp: Sat Feb 11 22:39:43 2006
Primary (Reporting) Cp: 115  Set: 1 Car: 2  Ref: yes  Event:   9923
Missing P:  Keep: 1  Phase: 0x7d10  Strength: 31
Secondary Sector Information:
Slot 1:   Keep: 1   offset: 391   Strength: 27   Ref: no
Slot 2:   Keep: 1   offset: 325   Strength: 38   Ref: no
[download]

Prints:

Primary (Reporting) Cp: 113  Set: 2 Car: 1  Ref: yes  Event:   9922
Primary (Reporting) Cp: 115  Set: 1 Car: 2  Ref: yes  Event:   9923
[download]

Note, this is not an attempt to solve you immediate problem - others have done that. It is simply a demonstration of a couple of coding tips.