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#!/usr/bin/perl print "Hello, World!\n"; The hash mark character introduces a comment in Perl, which runs up to the end of the line of code and is ignored by the compiler (except on Windows). The comment used here is of a special kind: it’s called the shebang line.
Perl is a language allowing many different styles of programming. A developer is as likely to find a module written in a procedural style (for example, Test::Simple ) as object-oriented (e.g. XML::Parser ), both are considered equally valid according to what the module needs to do.
#!usr/bin/perl – called the "shebang line", after the hash symbol (#) and ! (bang) at the beginning of the line. It is also known as the interpreter directive. # – the number sign, also called the hash symbol. In Perl, the # indicates the start of a comment. It instructs perl to ignore the rest of the line and not execute it as script code.
will fix the problem. This is actually a pretty common mistake, and perl will catch it for you if you turn "warnings" on. To do that, change the first line to: #!/usr/bin/perl -w and perl will say: Useless use of sort in void context at line 10. which is a little obscure, but at least tells you to look for trouble on that line.
The need to explain the what is a sign that it is too complex and should be re-worked. "Don't document bad code – rewrite it." [9] "Good comments don't repeat the code or explain it. They clarify its intent. Comments should explain, at a higher level of abstraction than the code, what you're trying to do." [10]
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.
CGI.pm is a large and once widely used Perl module for programming Common Gateway Interface (CGI) web applications, providing a consistent API for receiving and processing user input.
This includes Perl itself, nearly all publicly released modules, many scripts, most design documents, many articles on Perl.com and other Perl-related web sites, and the Parrot virtual machine. Pod is rarely read in the raw, although it is designed to be readable without the assistance of a formatting tool.