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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 ...
In other languages, variables are often initialized to known values when created. Examples include: VHDL initializes all standard variables into special 'U' value. It is used in simulation, for debugging, to let the user to know when the don't care initial values, through the multi-valued logic, affect the output.
Uninitialized data, both variables and constants, is instead in the BSS segment. Historically, to be able to support memory address spaces larger than the native size of the internal address register would allow, early CPUs implemented a system of segmentation whereby they would store a small set of indexes to use as offsets to certain areas.
The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language. A top level distinction from one language to another is whether the expressions permit side effects (as in most procedural languages) and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated (most standard ...
In the Perl programming language, autovivification is the automatic creation of new arrays and hashes as required every time an undefined value is dereferenced. Perl autovivification allows a programmer to refer to a structured variable, and arbitrary sub-elements of that structured variable, without expressly declaring the existence of the ...
Perl programmers may initialize a hash (or associative array) from a list of key/value pairs. If the keys are separated from the values with the => operator (sometimes called a fat comma ), rather than a comma, they may be unquoted (barewords [ 5 ] ).
Learning Perl, also known as the llama book, [1] is a tutorial book for the Perl programming language, and is published by O'Reilly Media. The first edition (1993) was authored solely by Randal L. Schwartz , and covered Perl 4.
The null coalescing operator is a binary operator that is part of the syntax for a basic conditional expression in several programming languages, such as (in alphabetical order): C# [1] since version 2.0, [2] Dart [3] since version 1.12.0, [4] PHP since version 7.0.0, [5] Perl since version 5.10 as logical defined-or, [6] PowerShell since 7.0.0, [7] and Swift [8] as nil-coalescing operator.