|o||Opening curly on same line as keyword, if possible, otherwise line up.|
|o||Space before the opening curly of a multi-line BLOCK.|
|o||One-line BLOCK may be put on one line, including curlies.|
|o||No space before the semicolon.|
|o||Semicolon omitted in short one-line BLOCK.|
|o||Space around most operators.|
|o||Space around a complex subscript (inside brackets).|
|o||Blank lines between chunks that do different things.|
|o||No space between function name and its opening parenthesis.|
|o||Space after each comma.|
|o||Long lines broken after an operator (except and and or).|
|o||Space after last parenthesis matching on current line.|
|o||Line up corresponding items vertically.|
|o||Omit redundant punctuation as long as clarity doesnt suffer.|
Here are some other more substantive style issues to think about:
Just because you CAN do something a particular way doesnt mean that
you SHOULD do it that way. Perl is designed to give you several
ways to do anything, so consider picking the most readable one. For
is better than
because the second way hides the main point of the statement in a modifier. On the other hand
is better than
Similarly, just because an operator lets you assume default arguments doesnt mean that you have to make use of the defaults. The defaults are there for lazy systems programmers writing one-shot programs. If you want your program to be readable, consider supplying the argument.
Along the same lines, just because you CAN omit parentheses in many places doesnt mean that you ought to:
Even if you arent in doubt, consider the mental welfare of the person who has to maintain the code after you, and who will probably put parentheses in the wrong place.
|o||Dont go through silly contortions to exit a loop at the top or the bottom, when Perl provides the last operator so you can exit in the middle. Just outdent it a little to make it more visible:|
|o||Dont be afraid to use loop labelstheyre there to enhance readability as well as to allow multilevel loop breaks. See the previous example.|
|o||Avoid using grep() (or map()) or backticks in a void context, that is, when you just throw away their return values. Those functions all have return values, so use them. Otherwise use a foreach() loop or the system() function instead.|
|o||For portability, when using features that may not be implemented on every machine, test the construct in an eval to see if it fails. If you know what version or patchlevel a particular feature was implemented, you can test $] ($PERL_VERSION in English) to see if it will be there. The Config module will also let you interrogate values determined by the <B>ConfigureB> program when Perl was installed.|
|o||Choose mnemonic identifiers. If you cant remember what mnemonic means, youve got a problem.|
While short identifiers like $gotit are probably ok, use underscores to
separate words in longer identifiers. It is generally easier to read
$var_names_like_this than $VarNamesLikeThis, especially for
non-native speakers of English. Its also a simple rule that works
consistently with VAR_NAMES_LIKE_THIS.
Package names are sometimes an exception to this rule. Perl informally reserves lowercase module names for pragma modules like integer and strict. Other modules should begin with a capital letter and use mixed case, but probably without underscores due to limitations in primitive file systems representations of module names as files that must fit into a few sparse bytes.
You may find it helpful to use letter case to indicate the scope
or nature of a variable. For example:
Function and method names seem to work best as all lowercase. E.g., $obj->as_string().
You can use a leading underscore to indicate that a variable or function should not be used outside the package that defined it.
|o||If you have a really hairy regular expression, use the /x modifier and put in some whitespace to make it look a little less like line noise. Dont use slash as a delimiter when your regexp has slashes or backslashes.|
|o||Use the new and and or operators to avoid having to parenthesize list operators so much, and to reduce the incidence of punctuation operators like && and ||. Call your subroutines as if they were functions or list operators to avoid excessive ampersands and parentheses.|
|o||Use here documents instead of repeated print() statements.|
Line up corresponding things vertically, especially if itd be too long
to fit on one line anyway.
Always check the return codes of system calls. Good error messages should
go to STDERR, include which program caused the problem, what the failed
system call and arguments were, and (VERY IMPORTANT) should contain the
standard system error message for what went wrong. Heres a simple but
Line up your transliterations when it makes sense:
|o||Think about reusability. Why waste brainpower on a one-shot when you might want to do something like it again? Consider generalizing your code. Consider writing a module or object class. Consider making your code run cleanly with use strict and use warnings (or <B>-wB>) in effect. Consider giving away your code. Consider changing your whole world view. Consider... oh, never mind.|
Try to document your code and use Pod formatting in a consistent way. Here
are commonly expected conventions:
|perl v5.22.1||PERLSTYLE (1)||2015-10-17|