I'm looking to create a custom field which is a Hyperlink, but the Hyperlink is a concatination of a static URL + regexp. Any ideas on how to do this? My regexp is correct, just need to concat the URL to it

I am having trouble with Hyperlinks today for some reason. You can try doing it the "Old" way, using a Free-Form Text formula like this:

'<a class="dottedlink" href="<https://static.url/>' || REGEXP_REPLACE({column}, 'e', '') || '" target="_blank">Link Text</a>'

You should be able to use any of the Oracle RegEx functions (REGEXP_COUNT, REGEXP_INSTR, REGEXP_LIKE, REGEXP_REPLACE, REGEXP_SUBSTR) in place of REGEXP_REPLACE.

Great thank you. Do I need to ticket the FORMULA box?

for this kind of formula, yes, formula should be set to true, and store value should be false.