Thanks for the feedback! as per your response, the difference in space escaping between Lucee and ACF doesn't affect functionality, as spaces aren't special characters in regular expressions. So, I'll close the ticket.

since “space literal” isn’t a special character on it’s own; and `\ ` isn’t a special sequence; there shouldn’t be any functional difference that I can think of.

I think functionally it makes no difference? What do you reckon Mr Regex!

, I have tested this ticket with Lucee version 6.2.1.25-SNAPSHOT. When I executed the reEscape() function, it now returns the string with escape characters for all regular expression special characters. However, when comparing it with ACF, there is a slight difference: in Lucee, spaces are also escaped, while in ACF, spaces are not treated as special characters and are not escaped

Return:
Lucee --- Hello\.\ How\ are\ you\?\ \(test\)\ \[123\]\ \{abc\}\ \^\$\.\*\+\?\|\\

ACF ----- Hello\. How are you\? \(test\) \[123\] \{abc\} \^\$\.\*\+\?\|\\