my (@memberlist, @allmembers);

foreach my $member (@memberlist) {
   open(FILE, "$member.dat")  or
      die "Open failed for file: '$member.dat'. $!\n";
   lock(FILE);
   my @members = <FILE>;
   unlock(FILE);
   close(FILE);
   chomp @members;
   push (@allmembers, join (" ", @members));
}