I think I would be tempted to try modifying IPC::Run->signal() to return the result of kill:

sub signal {
   my IPC::Run $self = shift ;

   local $cur_self = $self ;

   $self->_kill_kill_kill_pussycat_kill unless @_ ;

   Carp::cluck "Ignoring extra parameters passed to kill()" if @_ > 1 
+;

   my ( $signal ) = @_ ;
   my $rv;
   croak "Undefined signal passed to signal" unless defined $signal ;
   for ( grep $_->{PID} && ! defined $_->{RESULT}, @{$self->{KIDS}} ) 
+{
      _debug "sending $signal to $_->{PID}"
         if _debugging;
      $rv = kill $signal, $_->{PID}
         or _debugging && _debug "$! sending $signal to $_->{PID}" ;
   }
   
   return $rv;
}
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and then use that within your pump loop with a parameter of 0;

pump $h while $h->signal( 0 ) 
        and $out !~ /BRU Server >/i;
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That ought to terminate the loop if the process could not be signalled (has died).

Obviously untested, but if it works, you could suggest the modification to the maintainer.