my @lines;
while (length $_) {
  my $p=substr($=, 0, 1, '');
  while ($p ne ' ') {
    print "Remaining text: $_\n";
    print "p='$p'";
    die "line to short, but no previous line?"
      unless length $lines[-1];
    print "Previous line: $lines[-1]\n";
    $_=substr($lines[-1], -1, 1, '');
    $p=substr($_, 0, 1, '');
  }
}