my $IN = IO::File->new_tmpfile;

##</code><code>##

local *OUT;
open OUT, ">output.log";

##</code><code>##

sub callexternalpgm {
  my ( $cmd, $cmdargs, $rawdata, $processeddata, $err ) = @_;

  my ( $IN, $OUT, $ERR );

  $ERR = gensym();

  my $pid;
  eval{ $pid = open3( $IN, $OUT, $ERR, $cmd, @{ $cmdargs } ) };
  return $@ if $@;

  print $IN $rawdata;
  close $IN;

  my $select = new IO::Select;
  $select->add( $OUT, $ERR );

  while(my @ready = $select->can_read) {
    foreach my $fh (@ready) {
      my $data;
      my $length = sysread $fh, $data, 4096;

      if( ! defined $length || $length == 0 ) {
        $err .= "Error from child: $!\n" unless defined $length;
        $select->remove($fh);
      } else {
        if($fh == $OUT) {
           $processeddata .= $data;
        } elsif($fh == $ERR) {
          $err .= $data;
        } else {
          return undef;
        }
      }
    }
  }

  waitpid $pid, 0; # wait for it to die

  warn $err if $err;
  return 1;
}