regexMatcher in Column Expressions to identify fields with non-alphanumeric chars

I’m struggling with something that should be really simple. I want to use regexMatcher() in a Column Expressions node to evaluate true for records that contain chars other than alphanumeric, and evaluate false for fields with only regular alphanumeric chars.

Eg “This field 1234” → false

But “This - field” → true

ChatGPT is adamant that this expression should work, but unfortunately every record returns false even when I can see non alphanumeric chars:

regexMatcher(column("WORK_GROUP_DESC"), "[^a-zA-Z0-9]")

So what am I doing wrong? As usual I find regex functions in KNIME utterly baffling, and chatgpt is so often helpless. Typically, the function-specific help for regexMatch is also pretty useless, as is so often the way with this wonderful but patchily-documented platform - check out the total lack of explanation below