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A module defines its source code to be in a package (much like a Java package), the Perl mechanism for defining namespaces, e.g. CGI or Net::FTP or XML::Parser; the file structure mirrors the namespace structure (e.g. the source code for Net::FTP is in Net/FTP.pm).
Originally, filehandles could only be created with package variables, using the ALL_CAPS convention to distinguish it from other variables. Perl 5.6 and newer also accept a scalar variable, which will be set (autovivified) to a reference to an anonymous filehandle, in place of a named filehandle.
Such programs are called "scripts". In this regard, perl is considered to be a scripting language. Typical operations performed by shell scripts include program execution, printing text, and file manipulation (copying, renaming, deleting, etc.). Being an interpreted language, perl has the following advantages: Platform independence
In these languages, including the line __DATA__ (Perl) or __END__ (Ruby, old Perl) marks the end of the code segment and the start of the data segment. Only the contents prior to this line are executed, and the contents of the source file after this line are available as a file object: PACKAGE::DATA in Perl (e.g., main::DATA) and DATA in Ruby ...
In Perl, local variables are declared using the my operator. Uninitialized scalars will have the value undef; uninitialized arrays or hashes will be (). [5] Perl also has a local operator that does not create automatic variables, [6] instead giving global (package) variables a temporary value, which is dynamically scoped to the enclosing block ...
AWK (/ ɔː k / [4]) is a domain-specific language designed for text processing and typically used as a data extraction and reporting tool. Like sed and grep, it is a filter, [4] and it is a standard feature of most Unix-like operating systems.
Perl provides three loop control keywords that all accept an optional loop label as an argument. If no label is specified, the keywords act on the innermost loop. Within nested loops, the use of labels enables control to move from an inner loop to an outer one, or out of the outer loop altogether.
The Perl virtual machine is a stack-based process virtual machine implemented as an opcodes interpreter which runs previously compiled programs written in the Perl language. The opcodes interpreter is a part of the Perl interpreter, which also contains a compiler (lexer, parser and optimizer) in one executable file, commonly /usr/bin/perl on various Unix-like systems or perl.exe on Microsoft ...