Thank you for your insights. As I thought, it may be something behind my reach. The possibility to use HTML5+javascript is of course okay, as it is documented and so on, however it would mean to drop Perl. And my second goal was to apply my legacy Perl scripts "live" to the transcribed text (regex, data visualization, etc.) and do computations on the incoming text. This would mean to rewrite everything from scratch in javascript (a language I know only vaguely), which is, of course, not a nice thought.