Incomplete regex implementation

[ain]

I just came across a regex issue on ignoring XML error reports on Bad value 6d0a884808fd72fcdbac270585981015metadata3320 for attribute id on element metadata: Not a valid XML 1.0 name.

The regex used: Bad value [\w]+ for attribute id on element metadata: Not a valid XML 1.0 name.

The regex that actually worked: Bad value [A-Za-z0-9]+ for attribute id on element metadata: Not a valid XML 1.0 name.

In terms of regex, both should actually be equally usable, but unfortunately are not. I guess it's a slash issue?