The data you are processing looks like c program. You are right to use s modifier to take data as a single line.

I quickly come up with something, and hope it helps: (Well, I do not handle things like brackets in quotes, (unmatched) brackets in comments, but in your real code, you have to expect those)

use strict;
use warnings;

open(CPROG, "<test1.cpp");
my $concat_line;
while (my $line = <CPROG>) {
    if ($line =~ /\(/s) {
        $concat_line = $line;
    } else {
        $concat_line .= $line if ($concat_line);
    }
    if ($concat_line && ($concat_line =~ /\(.*\)/s)) {
        print $concat_line;
        $concat_line = undef;
    }
}
close(CPROG);
[download]

I tried it with

#include <string.h>
#include <stdio.h>

main() {
    char a[80];
    strcpy(a,
    "abcd");
    strcat(a,
    "\015");
    printf("%s", a);
}
[download]

And it gives me:

main() {
    strcpy(a,
    "abcd");
    strcat(a,
    "\015");
    printf("%s", a);
[download]