One would need to add some synchronizing code so the parent process can wait until first sysread is in progress. That way Perl won't eat any of the parent's output into its buffers for <DATA>.

That doesn't appear to be needed, but my tests haven't been extensive.

The second would be to change next unless /\s/ to next unless /\s$/

Oops, you're right that there's a problem with my solution. However, your fix is no good (If it receives "abc def ghi", it should output "abc def " and only leave "ghi" in the buffer). At this point, I'm not going to fix it. Just stick to your getc solution.

And thank you again, ikegami.

The need for the synchonizing code with sysread came from graff's observation that he needed to add a sleep 1; the first line or so of output gets lost unless the main script waits a bit before it sends anything.

I hadn't thought about spaces embedded in the password, but it would only be a problem if the script read more than one byte at a time. Using getc, $_ will never contain embedded whitespace, because it would have been found on a previous pass through the loop.

Last night you pointed out that checking for /\s/ (or /\s$/) doesn't work if the password contains spaces. After I though about it for a while, I think it can be fixed by changing

next unless /\s/;
[download]

to see if $_ is the beginning of the password

next if $_ eq substr "' . (quotemeta $password) . '", 0, length;
[download]

when reading one character at a time.

If it was really necessary to read more than one character at a time and the passwords would contain spaces, it would probably work to check if any trailing substring of the buffer matches any leading substring of the password like this:

[[... beginning of the code as above...]]
print '
  use warnings;
  use strict;
  use List::Util qw(min);
  select STDOUT;
  $| = 1;
  my $chr;
  $_ = "";
CHAR:
  while (defined ($chr = getc DATA)) {
      $_ .= $chr;
      foreach my $n (1..min ' . (length $password) . ', length) {
          next CHAR if substr ("' . (quotemeta $password) . '", 0, $n)
            eq substr ($_, (length)-$n, $n);
      }
      s/' . (quotemeta $password) . '/removed/ig;
      print;
      $_ = "";
  }
  print;
  __DATA__
';
[[... the rest of the code is as above...]]
[download]

... but I think I prefer the simplicity of reading one character at a time.

Take care,

quester