sub stripPOS {
  my $words = shift;
  # rip out any / plus following characters, up to the 
  # first space
  $words =~ s!/\S*!!g;
  return $words;
}
  $sentence =~
    s! \s \<NP\d*\> (.*?) \</NP\> \s ! stripPOS($1). '/NP' !egx;