G'day adrya407,

Whenever you find yourself in this position — needing to access multi-line blocks of data delimited by known or calculable boundaries — consider using one of the Range Operators. Here's an example which successfully handles all three of your posted formats: 

#!/usr/bin/env perl

use strict;
use warnings;

my $start_re = qr{(?x: ^ my_variable = )};
my $end_re   = qr{(?x: (?<! ^ my_variable ) =
                     | ^ \[ [^\]]* \] $
                     | ^ [*]{3} \s+ Block \s+ \d+
                )};

while (<DATA>) {
    print if /$start_re/ .. /$end_re/ && next;
}

[download]

__DATA__, and the same test data posted in the OP, are in the spoiler:

<Reveal this spoiler or all in this thread>

Output:

my_variable=important_content_section1
important_content_section2
important_content_section3
my_variable=important_content_section1
important_content_section2
important_content_section3
my_variable=important_content_section1
important_content_section2
important_content_section3

[download]

I think that also covers most of the points from your update.

See also "perlre: Extended Patterns", which has details of the regex constructs I've used — such as (?x: pattern ) and (?<! pattern ) — and many more like them.

— Ken

In reply to Re: Multiline regex by kcott
in thread Multiline regex by adrya407

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.