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In computer programming languages, a switch statement is a type of selection control mechanism used to allow the value of a variable or expression to change the control flow of program execution via search and map. Switch statements function somewhat similarly to the if statement used in programming languages like C/C++, C#, Visual Basic .NET ...
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 ".
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.
Switch statements can allow compiler optimizations, such as lookup tables. In dynamic languages, the cases may not be limited to constant expressions, and might extend to pattern matching, as in the shell script example on the right, where the *) implements the default case as a glob matching any string.
If-then-else flow diagram A nested if–then–else flow diagram. In computer science, conditionals (that is, conditional statements, conditional expressions and conditional constructs) are programming language constructs that perform different computations or actions or return different values depending on the value of a Boolean expression, called a condition.
Perl and Ruby overload the ".." operator in scalar context as a flip-flop operator - a stateful bistable Boolean test, roughly equivalent to "true while x but not yet y", similarly to the "," operator in sed and AWK. [1] GNU C compatible compilers have an extension to the C and C++ language to allow case ranges in switch statements:
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.
Most programming languages are not standardized by an international (or national) standard, even widely used ones, such as Perl or Standard ML (despite the name). Notable standardized programming languages include ALGOL , C , C++ , JavaScript (under the name ECMAScript ), Smalltalk , Prolog , Common Lisp , Scheme ( IEEE standard), ISLISP , Ada ...