in reply to Some Help for a Report About Perl
Maintainability is the nebulous measurement of how easy it is to understand and modify a program. Write some code. Come back to it in six months (or six days). How long does it take you to find and fix a bug or add a feature? That's maintainability.
Maintainability doesn't measure whether you have to look up the syntax for a builtin or a library function. It doesn't measure how someone who has never programmed before will or won't read your code. Assume you're talking to a competent programmer who understands the problem you're trying to solve. How much work does she have to put in to understand your code? What problems will she face in doing so?
Oh, one more thing. Don't fall for the old chestnut that "Python is more readable than Perl". Or that "Perl looks like line noise". Instead, remind anyone who makes such a claim that Russian is "unreadable" if you don't know Russian. Then further challenge them to explain how Python's magical powers of readability ensures that they:
That is, "readability" is far less important than "maintainability" -- so that programmers who know the language can come to the code later in its life and understand its construction and intentions and change it comfortably and confidently. And writing "maintainable" Perl is just as easy as writing "maintainable" Python.
Update: Computer programming (wikipedia) defines Readability as "the ease with which a human reader can comprehend the purpose, control flow, and operation of source code" and further lists factors that affect it namely: following a consistent programming style (and naming conventions), correct indentation, judicious commenting and wise decomposition. Note that these important code qualities are essentially independent of the programming language being used.
References Added Later