On the same subject, don't forget about the "x"-modifier for regexen. It basically allows you to split a regex into multiple lines and comment on every line.

Allow me to quote from perlman:perlfaq6, Section 1

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/x lets you turn this:

    s{<(?:[^>'"]*|".*?"|'.*?')+>}{}gs;
[download]

into this:

    s{ <                    # opening angle bracket
        (?:                 # Non-backreffing grouping paren
             [^>'"] *       # 0 or more things that are neither > nor 
+' nor "
                |           #    or else
             ".*?"          # a section between double quotes (stingy 
+match)
                |           #    or else
             '.*?'          # a section between single quotes (stingy 
+match)
        ) +                 #   all occurring one or more times
       >                    # closing angle bracket
    }{}gsx;                 # replace with nothing, i.e. delete
[download]

It's still not quite so clear as prose, but it is very useful for describing the meaning of each part of the pattern.

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Again, hope that helps,
Brother Ade