Question

I’m in the process of trying to learn more about regular expressions and I’ve been wondering about the following:

How to insert a space after a dot character, but only when the dot character is not surrounded by numbers, e.g. it needs to match . but not 22.22!

Answer 1

This is a nice case of zero-width assertions:

$subject =~ 
    s/(?<=\.         # after a dot,
        (?!          # but not matching
          (?<=\d\.)  # digit followed by dot before, AND
          (?=\d)     # digit afterward
        )
      )/ /x
    g;

I think that you will find the comments self explanatory! 🙂