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$variableis a normal scalar is an array and %variableis an associative array. Instead of declaring a variable one preceeds it with a spcial charachter. There are scalar variables, one and two dimensional arrays and associativeĪrrays. The enormous value of that feature should be evident. Gives the number of elements in a scalar context and the elements itself Which makes it uniqe and more usful then most other script languages.Ī soubroutine can return lists and not only scalars like in C. That perl distinguishes between scalar and list context is the big feature, Quote something wich contains "/": qq!/usr/bin/$file Quote a quoted string: qq/"$name" is $name/ Quote a list of words: ('term1','term2','term3')or: qw/term1 term2 term3/
#PERL CODING CODE#
Perl can include other programming code with: require With a "sub" and enclosed in a block like: sub Perl knows it's a soubroutine if it the code is preceeded But soubroutinesĬan be placed anywhere and will only be evaluated when called from a normalĬommandline. Normal commands are executed in the order written in the script. So one can continue a command over several lines and terminates it only
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Start with the first non space charachter on a line and end with a " ". To the end of the line is comment and has no effect on the program. That unix knows that it is a perl script there must be the following headerĪt the topline of every perl script: #!/usr/bin/perlwhere the path to perl has to be correct and the line must not exeedĪfter the header line: #!/usr/bin/perlthereĪre either empty lines with no effect or commandlines or commentary lines. Perl is a script language, which is compiled each time before running. Pipe input and ouput from/to Unix Commandsīuilding a Socket Connectin to another Computer If a function has a non-obvious return semantic, document type and semantic of the possible return values.Processing files mentioned on the Commandline Use enough comments in the code to make it understandable.ĭocument Function Behaviour (ClearBehave)Īs far as the behaviour of a function is not clear by its name and parameters, document that behaviour. Use the forward slash as path separator in all cases.Įxception: When a system program needs a path in local convention as argument. Use the Correct Comparison Operators (Compare) Use and assign regular expression backinserters (like ($1), ($2)) as close to the originating expression as possible, never more than five lines away.Ĭheck the return values of all system calls. Possible exceptions: standard perl idioms.ĭon't forget to close all filehandles and connections. Use an explicit return statement for every return. Implementation Details Explicit Returns (Return) Recommendation: use ref postfix for references prefere underscores instead of mixed cases for variable names: multipart_name.start class names with a capital: MySelfmadeModule.Use my to scope all variables local to a block.Īssign all parameters of a function to local, sensibly named variables on top of the function body. Prefer perl functionality over calls to system() where possible.ĭon't do smaller optimizations, if they make the code less readable and there is no proven reason.ĭeclarations: Scoping and Names Use my (My) However, don't create new dependencies to uncommon Perl modules, if there is no major need.
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Use the modules provided in a standard Perl 5.8 installation instead of reinventing the wheel. Put common code into an extra function.ĭuplicate code may be okay, if otherwise dependencies among so far unrelated modules would be created. A comment line or large control structures are hints to extract functions, making the containing function more concise and readable.Īvoid and remove duplicate code.
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Rules for Perl General Strict Settings (Strict)Īpply use strict and use warnings to all scripts and modules. die 'Cant open foo: ' unless open(my fh, <, foo) because the second way hides the main point of the statement in a modifier. open(my fh, <, foo) die 'Cant open foo: ' is better than. See the C++ Coding Standards for the general purpose of Standards.Īfter doing Code Reviews with C++ for a while, there occurred the wish among Perl developers to do code reviews as well and to set up a rule set for that purpose. Perl is designed to give you several ways to do anything, so consider picking the most readable one. 2.5.2 Document Function Behaviour (ClearBehave).2.4.6 Use the Correct Comparison Operators (Compare).2.3.3 Assign Parameters at Top (Params).