Search API: Support for start/end anchors (eg ^/$ regex)

In https://www.dropboxforum.com/hc/en-us/community/posts/203590593-Search-API-More-than-1000-results-pages-offsets-pointers- I asked about the 1000-item limit on the search API.

If there's no way around it, one option could be to do a more precise search with start/end anchors.  eg searching for ".xls" matches all ".xlsx" files, and if my user has more than 1000 xlsx files, I can't find the xls files.  

However, if I could specify end-of-line anchors, I could search for ".xls$" and ".xlsx$" independently.

Is something like this supported?