Hi there.
I've just taken elfeed out for a spin. Thanks for this!
I'm looking at the RSS feed for BC highways.
https://www.drivebc.ca/api/events/region/kootenays?format=rss

Suppose I want to filter articles by those that match only "Highway 1"

if I hit s, and then enter 
Highway 1

I also see highway 91, etc.

So I try:
Highway[:blank:]1

this doesn't match anything. I google a while, give up, email you..

In regexp syntax, "[:…:]" by itself is a plain old bracket expression. If 
you want to reference a named character class, you must put that inside a 
bracket expression: "Highway[[:blank:]]1" That works when I try it.

Tokenizing the search query and treating tokens as regexps is admittedly 
awkward. I wish I had come up with something that worked more intuitively.