Using nginx on an OpenMediaVault (debian) server and trying to set up a Location with regex match and wanted to match 3 actual characters. I should (certainly in PCRE) have been able to use:-

\w{3}

However with this I was unable to restart nginx. \w\w\w was OK, as was ... and even ..+, but any use of {} as a fixed number of occurrences, or range etc and nginx refused to start.

Is there some magic pixie dust required in order to be able to use these basic regex functions?