my %seen = (); # keyed by URL, contains times
  while ( <line> ) {
    if ( line =~ m/(date)(action)(URL)/ ) {
      if ( action == "played" ) {
        seen{URL} = date;
      } elsif ( action == "stopped" ) {
        duration = date - seen{URL};
        print( "URL: duration" );
      }
    }
  }