use warnings;
use strict;

my $password = "hide_me";
my $log_file = "test.log";
open STDOUT, "| perl | tee -a $log_file";

my $script = <<_END_FILTER_SCRIPT_;
  use warnings;
  use strict;
  my \$chr;
  \$_ = '';
  while (sysread DATA, \$chr, 1) {
      \$_ .= \$chr;
      if ( /\\s\$/ ) {
          s/\Q$password\E/removed/ig;
          syswrite STDOUT, \$_;
          \$_ = '';
      }
  }
  close STDOUT;
  __DATA__
_END_FILTER_SCRIPT_

syswrite STDOUT, $script;
sleep 1;  ## had to add this delay so next syswrite would always work

syswrite STDOUT, "The password is $password\n";
foreach (qw{Output is unbuffered if these words are printed one at a time.}) {
        syswrite STDOUT, $_." ";
        sleep 1;
}
syswrite STDOUT, "\n";
sleep 1;
syswrite STDOUT, "Output is line buffered if the last line came out all at once.\n";
close STDOUT;