Just to add to dmm's code. If you don't really care about scrolling and buffering the output, you could use this for the write to window:

#!/usr/local/bin/perl -w

# Something like this:
use IO::Select;
use Curses;

my $win = new Curses;
my $x   = $win->getmaxx;
my $y   = $win->getmaxy;
my $m   = int( $y/2 );
my $r   = $x-2;
my $div = "-"x$r;

my $one_s = 1;
my $one_e = $m-1;
my $two_s = $m+1;
my $two_e = $y-2;

$win->box( '|', '-' );
$win->addstr( $m, 1, $div );
$win->refresh;

my $bladeenc_cmd = 'bladeenc -whatever args';
my $cdparanoia_cmd = 'cdparanoia -whatever else args';

open P1, "$bladeenc_cmd|" or die "bladeenc: $!";
open P2, "$cdparanoia_cmd|" or die "cdparanoia: $!";

local $SIG{PIPE} = sub { warn "pipe closed"; };

my $s = IO::Select->new();
my $timeout = 100;    # msec(?)

$s->add(\*P1);
$s->add(\*P2);

my $one_cnt = $one_s;
my $two_cnt = $two_s;

my @ready;
while (@ready = $s->can_read($timeout)) {
  foreach my $fh (@ready) {
     if ($fh == \*P1) {
       my $line = <$fh>;
       if( $line ) {
         $win->addstr( $one_cnt, 1, $line );
         $one_cnt++;
         $one_cnt = $one_s if $one_cnt > $one_e;
         $win->refresh;
       }
     }
     if ($fh == \*P2) {
       my $line = <$fh>;
       if( $line ) {
         $win->addstr( $two_cnt, 1, $line );
         $two_cnt++;
         $two_cnt = $two_s if $two_cnt > $two_e;
         $win->refresh;
       }
     }
   }
}
[download]

It's not pretty but it does work.

derby