...
        print "doing waitpid($pid,0)...\n";   # <---
        waitpid($pid,0);

##</code><code>##

17001 pts/16   S+     0:00          \_ /usr/bin/perl ./810377.pl
17002 pts/16   S+     0:00              \_ /usr/bin/perl ./810377.pl
17004 pts/16   S+     0:00                  \_ /usr/bin/perl ./810377.pl
17005 pts/16   S+     0:00                      \_ /usr/bin/perl ./810377.pl
17007 pts/16   S+     0:00                          \_ /usr/bin/perl ./810377.pl
17008 pts/16   S+     0:00                              \_ /usr/bin/perl ./810377.pl
17009 pts/16   S+     0:00                                  \_ /usr/bin/perl ./810377.pl
17018 pts/16   S+     0:00                                      \_ /usr/bin/perl ./810377.pl
17021 pts/16   S+     0:00                                          \_ /usr/bin/perl ./810377.pl
17054 pts/16   R+     0:03                                              \_ /usr/bin/perl ./810377.pl

##</code><code>##

        if ( $pid == 0 ) {
            if ( ! -e $lck ) {
                ...
            }
            else {
                ...
            }
            $SIG{INT} = 'DEFAULT';
            exit;   # <---
        }