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Most languages support multi-line block (a.k.a. stream) and/or single line comments. A block comment is delimited with text that marks the start and end of comment text. It can span multiple lines or occupy any part of a line. Some languages allow block comments to be recursively nested inside one another, but others do not.
Perl. Block comments in Perl are considered part of the documentation, and are given the name Plain Old Documentation (POD). Technically, Perl does not have a convention for including block comments in source code, but POD is routinely used as a workaround. PHP. PHP supports standard C/C++ style comments, but supports Perl style as well. Python
Easy to incorporate sample code; Easy to read without a pod formatter (i.e. in its source-code form) Easy to write in; An extended version of pod that supports tables and footnotes called PseudoPOD has been used by O'Reilly & Associates to produce several Perl books, most notably Programming Perl by Larry Wall, Tom Christiansen, and Jon Orwant.
The label block construct is a bit of an oddity: Perl treats a bare block – with or without a label – as a loop that is executed once. This means that the loop control keywords can be used to restart the block or to exit it prematurely; a bare block can also have a continue block.
The rules a compiler applies to the source creates implicit standards. For example, Python code is much more consistently indented than, say Perl, because whitespace (indentation) is actually significant to the interpreter. Python does not use the brace syntax Perl uses to delimit functions. Changes in indentation serve as the delimiters.
The structure of the Perl programming language encompasses both the syntactical rules of the language and the general ways in which programs are organized. Perl's design philosophy is expressed in the commonly cited motto "there's more than one way to do it".
The first line is a shebang, which identifies the file as a Perl script that can be executed directly on the command line on Unix/Linux systems. The other two are pragmas turning on warnings and strict mode, which are mandated by fashionable Perl programming style. This next example is a C/C++ programming language boilerplate, #include guard.
This comparison of programming languages compares how object-oriented programming languages such as C++, Java, Smalltalk, Object Pascal, Perl, Python, and others manipulate data structures. Object construction and destruction