Replacing text with a regular expression. How right?

Question

Regular Expressions

There is a text: abc:ABCD It is necessary
that it turns out like this: abc :
aBCD , and subsequent CAPSOM?

Answer 1

^(.*)([:|;])([A-Z])([A-Z]*)$replaced by\1\2\L\3\U\4

Answer 2

If you are talking about a programming language, then write a callback function that will accept the search result and return the result.
In it, and make the conversion to lower case of the first character after :

Answer 3

^(.*[:|;])([A-Z])([A-Z]*)$
change to
$1\L$2\U$3