Why am I getting this error when using regex for URI search?

[ghildiya]

I have the following query to search results which contain a specific rest endpoint which has a UUID path parameter:

.... | regex requestURI="/baseurl/\b[0-9a-f]{8}\b-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-\b[0-9a-f]{12}\b

But it seems to be wrong. Error is :

Unknown search command '0'.

What is the mistake I am making here?

[richgalloway]

Splunk appears to be interpreting part of your regular expression as a subsearch. Make sure the expression is enclosed in quotation marks and any embedded quotation marks are escaped.

[ghildiya]

I tried this:

.... | regex requestURI=*/baseurl/\"[0-9a-f]{8}\b-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-\b[0-9a-f]{12}\"*

But this too doesn't work. 

[richgalloway]

The regex command is still missing the enclosing quotation marks.