Case, you're a miracle worker, THANKS for this! Just the %dartist% and %dtitle% seem to work fine on their own by changing the nominal %artist% and %title% in the Run Services expression. Furthermore, it doesn't effect the search working the same way on a PLAYING regular file instead of a stream. If the file was not being played, one would probably need to use your example of $if2(%dtitle%,%title%) in the right fields for the variable code to work.
I listen to a lot of Internet radio, and when a song comes on I'm curious about, with foo_dyndec I NOW can use Run Services to perform a search on the playing track's artist, or artist + song, at various sites. Surely, this will be useful to many other Foobar users as well?! Just to get someone started, here's two Run Services entries that will search a playing radio stream's metadata at the Metal Archives website:
Metal Archives Artist (dyn)
https://www.metal-archives.com/search?searchString=$replace(%dartist%, ,+)&type=band_name
Metal Archives Artist + Title (dyn)
https://www.metal-archives.com/search/advanced/searching/songs?songTitle=$replace(%dtitle%, ,+)&bandName=$replace(%dartist%, ,+)&releaseTitle=&lyrics=&genre=#songs
Sir, this is the best plugin I've discovered in a long time! Thanks again.