Yes, yes. Another usecase I ran into a lot was having lat/long within the same XML field, this would have been really useful. I guess if the matcher fails the fields/colums firstName and secondName are undefined? However although the above is neat and clean it can of course now be done as follows:-
<field column="firstName" regex="Mr(\w*)\b\w*" replaceWith="$1" sourceColName="full_name"/>
<field column="secondName" regex="Mr\w*\b(\w*)" replaceWith="$1" sourceColName="full_name"/>
Also I would think the following will be a related common usecase; imagine a field which listed an indeterminate number of aliases or alternate names for a person. This is bad data design but it happens. We need to expose regex's global feature
<field column="alias" regex="([^,]+)" regex_options="global" sourceColName="aliases"/>
which would populate the column alias with multiple values. The attribute regex_options allows other regex options such as case insensitivity to be added as well.