raise statement, how to do multi-line message

Most of my raise statements use short format strings, but every now and then I get a long one that
wraps around in my code and looks ugly. Example:

raise exception 'Delivery specification for Monitored Event [%:%:%] and Notification Template [%] does not exist.',
p_event, p_monitor, p_subscriber, p_template;

Also, assume that I've got this indented a few levels, so that he format string wraps in my code.

Is there any way to break the format string into multiple lines in my code, but still
have a single line message (no line breaks) appear on the console?

I tried this, but it didn't work:

raise exception 'Delivery specification for Monitored Event' || '[%:%:%] and Notification Template [%] does not exist.',
p_event, p_monitor, p_subscriber, p_template;

It's not that big of a deal, but maybe there's a cool trick I need to learn...

- Leon