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    <p>When you open a file for reading, the file is by default read line by line. This is because the input record separator <code>$/</code> is set to newline. </p> <p>Since you are breaking each "line" on newline, it stands to reason that you can never find two newlines in a row in a single line.</p> <p>One way to get around this is, as Zaid has said, to change the input record separator with the <code>-0</code> flag. As long as the new input record separator is not partially matched by your regex, you will be fine. (As long as you do not try to match <code>.</code> to <code>\n</code>).</p> <p>Let's make your regex a bit less horrid. You don't need to escape <code>#</code>, unless you are using the <code>/x</code> modifier. You don't need to use several <code>#</code> characters in a row, use a quantifier, <code>+, * or {x,y}</code>. </p> <p>Instead of removing a string and then putting back an identical one, there are options to avoid typing the same thing twice. </p> <ul> <li>You can avoid removing the string by using <a href="http://perldoc.perl.org/perlre.html#Look-Around-Assertions" rel="nofollow">Lookaround Assertions</a>.</li> <li>You can use <code>\K</code> as a simplified Look-behind assertion (see above)</li> <li>You can capture strings and put them back using <code>$1, $2 ...</code>.</li> </ul> <p>My preference in this case would be to use a look-behind assertion to find the "color\n\n" string, then a look-ahead to find the "Color" comment.</p> <pre><code>perl -0777 -pwe 's/(?&lt;=color\n\n)(?=[#\s]+Color)/INSERT\n\n/' /path/to/file </code></pre> <p>Where <code>INSERT</code> is of course your text to insert, which I removed for readability. I also removed the <code>-i</code> flag so you can try it out first.</p>
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    1. POHow can I search for two sequential newlines (\n) using perl?
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    1. POHow can I search for two sequential newlines (\n) using perl?
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    1. COI will give that a shot, thanks. I assumed I needed to escape all hashes so it wouldn't be interpreted as a comment when run from a shell script. My solution, as you noted, is horrid. Your use of capture strings is much more elegant. I'm only about 2 days into perl and have a lot to learn.
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    2. CO@user30441 It's not capture, it's look-around assertions. When used in a shell script, meta characters can become troublesome. It might be a whole lot easier to just put the code in a script and call that. E.g. `perl /home/script.pl`.
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    3. COThanks for the clarification. I'm trying to avoid calling any outside scripts and your method worked well.
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