Regex to check all occurrences of specific letters be capital

Question

I'm trying to create a regex pattern that follows the rules:

1. All occurrence of the letters E, I, L must be capital strictly.
2. All other letters must strictly be lowercase.

I'm working with this rule ^[^eil]*[eil][^eil]*$ but having all capital letters also accepts the string.

Answer 1

You might use a match for only E I L, lowercase chars a-z without e i l plus digits _ and non word characters \W

^[EILabcdfghjkm-z0-9_\W]+$

Regex demo