If your text looks remotely like Perl, then Text::Balanced is worth a look. That module used to be part of the Parse::RecDescent distribution — it takes care of extracting the "Perl rules code" out of the grammars — but now it is a separate distribution. 
#!/usr/bin/perl
use Text::Balanced 'extract_bracketed';

$_ = <<'#END#';
This stays

onValidate
   {
    stuff in here
    {
       other stuff
    }
   }

This stays too
#END#

if(/onValidate/) {
    print substr($_, 0, $-[0]);   # before
    my ($extracted, $remainder) = extract_bracketed(substr($_, $+[0]),
+ '{}');
    print $remainder;             # after
    print "\n## extracted: ##\n$extracted\n";
}

[download]
which produces: 
This stays



This stays too

## extracted: ##
{
    stuff in here
    {
       other stuff
    }
   }

In reply to Re: pattern matching nested { }'s by bart
in thread pattern matching nested { }'s by Gerard

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.