Perl closes file on me.

pipe( GETPID, SENDPID );
SENDPID->autoflush(1);

$^F = fileno(SENDPID)
  if ( $^F < fileno(SENDPID) );
push my @cpid, fork_ok(
    1,
    sub {
        close(GETPID);
        $^F = fileno(SENDPID)
          if ( $^F < fileno(SENDPID) );
        my $r =
          system( 'lsof -np $$; echo $$ >&'
              . fileno(SENDPID)
              . '; exec src/ihlt >&2' );
        ok( $r == 2, 'ihlt: quit' );
    }
);