Update::I forgot to mention - you need to slurp the file, as hipowls(++) indicates below.

Your regex needs two changes:

• Escape the period
• Add the \s modifier.
         From "perldoc perlre":
             Used together, as /ms, they let the "." match any character whatsoever, while still allowing "^" and "$" to match, respectively, just after and just before newlines within the string.

This works:

s/^(if.*rctladm\.conf.*fi)/$1\n$here/sm;
[download]

However, may I suggest the following alternatives:

• Replace the entire shell script with perl.
• Insert a line at the end of the original script, that calls another (bash) script. Use perl to generate the second script. This way, the first script remains unmodified - easier to enhance and debug.