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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.
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.
#!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.
#!/usr/bin/perl # Loads the module and imports any functions into our namespace # (defaults to "main") exported by the module. Hello::World exports # hello() by default. Exports can usually be controlled by the caller. use Hello::World; print hello (); # prints "Hello, world!\n" print hello ("Milky Way"); # prints "Hello, Milky Way!\n"
The best-known is the string "From " (including trailing space) at the beginning of a line, used to separate mail messages in the mbox file format. By using a binary-to-text encoding on messages that are already plain text, then decoding on the other end, one can make such systems appear to be completely transparent .
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]
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.
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.