Hello,

I believe there is a regression with the regular expression syntax with something that I think used to work on 5.4 and no longer does on 6.4 when specifying the regular expression that matches the literal . (dot) character.

As per regular expression traditional syntax, the . should be escaped with a \ backslash (otherwise it matches any character). But it doesn't seem to work. (A work around is to use [.], but well, the backslash syntax is still a regression)

Steps to reproduce

create a calculated item with one of the four different formulas:

count(//agent.ping,#10,"regexp", "[.]")

returns 0, as expected

count(//agent.version,#10,"regexp", "[.]")

returns 10, as expected

count(//agent.version,#10,"regexp", "\\.")

returns 0 <- this is not expected, it should be 10, such as previous test

count(//agent.version,#10,"regexp", "\.")

rejected by frontend,  which is expected behavior as per double escape rule

two formulas rightfully work

one formula is rightly rejected

one formula produces the unexpected result