I need help with a regular expression that contains a look ahead. I have the following code that ignores my “not expression”. If I change the ! to an =, then it only matches the lines that contain TEXT. What I’m looking for are all lines that begin with only L1 and L3, but don’t contain the word TEXT. Is this possible using 1 regular expression? I thought that is what the look ahead function does. Thanks for any assistance. 
Code Snippet:

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

while (<DATA>) {
 chomp;
 if (/^(L[13].*(?:(?!TEXT).*).*)/) {print "$_\n";}
}
__DATA__
L1 04:10:07.915  LOG:   Want this Line1
L3 04:10:07.915  LOG:   Want this Line2
L1 04:10:08.024  LOG:   TEXT. Do not want this Line3
L3 06:37:58.163  LOG:   TEXT. Do not want this Line4
L3 07:02:36.921  LOG:   Want this Line5
L4 08:02:30.910  LOG:   Do not want this Line6
L5 08:02:36.943  LOG:   Do not want this Line7
L6 09:02:38.811  LOG:   Do not want this Line8
__END__  

 
Expected:
L1 04:10:07.915  LOG:   Want this Line1
L3 04:10:07.915  LOG:   Want this Line2
L3 07:02:36.921  LOG:   Want this Line5

But get:
L1 04:10:07.915  LOG:   Want this Line1
L3 04:10:07.915  LOG:   Want this Line2
L1 04:10:08.024  LOG:   TEXT. Do not want this Line3
L3 06:37:58.163  LOG:   TEXT. Do not want this Line4
L3 07:02:36.921  LOG:   Want this Line5

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In reply to RegEx Question - I want a line that contains this, but not this by mmontemuro

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