I'm not sure how to help you with your Parse::RecDescent problem (I've never used it), but here is a pure-regex solution that I whipped up (half to help, half for fun) for your original problem:

my $data = join('',<DATA>);
my $quoted_string =
qr/
    "
    (?:
        (?: [^"]* )
        |
        (?: (?<= \\ ) " )
    )*
    "
/x;
my $balenced_brackets =
qr/
    \{
    (?:
        (?> [^{}"] *)
        |
        (??{$quoted_string})
        |
        (??{$balenced_brackets})
    )*
    \}
/x;
my $function_header = qr/ function \s+ \w+ \s* \( [^)]* \) \s* /x;

my @matches = $data =~ /($function_header $balenced_brackets)/gx;
print join("\n\n",@matches);
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It worked with the sample code that you provided, but I have a feeling it will blow up when presented when it encounters something whacky (an unclosed brace, a brace inside quotes, etc). Consider it a preliminary solution :)

Update I added a bit of robustness to consider the case of the unclosed brace, but it now needs  re 'eval'. I also added a bit of explanation... Its still going to blow up on a brace inside quotes, however...

Update: Update: With some better structure, it can now handle brackets in quotes with no problem.