1st substitute/([A-Z][a-z][\W][\b])/<userinput>/;

The critical thing to remember about  [...] character classes is that most regex metacharacters are not meta-special inside them. Thus,  [.] (which you have used elsewhere) matches a single  '.' (period) character and  [\b] matches a single backspace control-character. So the pattern above might be described as:

•  [A-Z] A single upper-case character; followed by
•  [a-z] A single lower-case character; followed by
•  [\W] A single character that is anything not matching a  \w 'word' character (\W is a class onto itself, so no enclosing square brackets are needed); followed by
•  [\b] A single backspace control character.

Is any of that what you really wanted?

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