Re^2: Reguar expression

[citromatik]

That's not very complicated:

Well, maybe, but you are not asking the OP. That is: "I need a regular expression to match the following pattern.". You are using 2. (and perliff above uses 3!).

Update: Solving the problem with 2+ regexps is more or less trivial, but using just 1 is far more interesting. Here is a solution using look-ahead assertions (see perlre):

my $re = qr{ ^           # match at the beginning.
             (?!         # Look-ahead assertion: Fail if the next matc
+hes
               .* first  # match "first" everywhere except at the begi
+nning of the string
             )           # end of look-ahead assertion
             This .* \.  # Match "This" (at the beginning), followed b
+y anything and a dot
             $           # Match the end of a string.
         }x;             # Allow these comments