#!/usr/bin/perl
use warnings;
use strict;
use v5.10.0;

my $rx_consecutive = qr/
    ^ }
    (?:
        (?! ^ [{}] )
        .
    )*
    ^ }
/msx;

my @strings = split /!/, <<'STRINGS';
f()
{
    fred();
}

g()
{
    jim();
}
!
f()
{
    fred();
}

int i = 0;

}

g()
{
    jim();
}
!
f()
{
    if (i) {
        fred();
    }
}

g()
{
    jim();
}
STRINGS

for my $text (@strings) {
    say "Testing:\n$text\n";
    my $found = $text =~ $rx_consecutive;
    say "Double right-curly ", ($found? "found": "not found");
}
[download]

Thanks! Exactly what I was looking for. I am humbled by your wisdom and in awe of the beauty of your answer.

This regex: /}.*(?!{)}/ will do what you want I believe.

It'll match }} and }adfa} but not }{} or }asdf{asdf} etc.

Won't that mach a right-curly, followed by any-number-of-any-characters, followed by not-a-left-curly? Isn't a left-curly included in any-number-of-any-characters?

-QM
--
Quantum Mechanics: The dreams stuff is made of

No, at least not as how I understand it. The (?!{) is a negative-lookahead, meaning match any characters non-greedily as long as they do NOT contain a {, before the next }.

If I'm wrong, someone will inform me ;)

I guess I was unclear in my original post. I am dealing with multiple lines slurped up into a single string. The curlies I am looking for will have \n embedded in the string before them, so I have to use either \n or ^ in the expression along with s and m modifiers.

Any wisdom would be appreciated.

Switch to XML :) Let somebody else parse the c++ :)

There is a GCC-XML but it has been succeeded by CastXML is a C-family abstract syntax tree XML output tool. It reads c/c++/cpp/cxx... and outputs xml , xml is easy to read with XML::LibXML, xpather.pl , Re: XML::LibXSLT ignoring namespace on some Win32 machines (libxslt-1.1.27 bug), Re^5: Xpath not working, Re^8: How to parse xml with namespase vale in XMl:LibXML? (autoRegisterNs ), Re: XML::LibXML and namespaces, Re^2: Namespaced XML::LibXML XPath query (not a bug)

May I also cautiously suggest that you might be “implementing a language parser, the hard way.”   The CPAN library contains both very-powerful lexers/parsers that are written in Perl, and interfaces to well-known legacy systems.   Perhaps by using one of these tools you can dramatically change (for the better ...) your approach to this problem.   Several LALR-grammars for the C++ language, for example, are already available off-the-shelf.

As much as I like CPAN, I cannot load any of it on to the workstations at work. I am stuck with what I have and any other needed functionality has to be created by me. At least they finally upgraded from Perl 5.005!