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Perl in a Nutshell
book

Perl in a Nutshell

by Nathan Patwardhan, Ellen Siever, Stephen Spainhour
December 1998
Beginner to intermediate content levelBeginner to intermediate
674 pages
40h 41m
English
O'Reilly Media, Inc.
Content preview from Perl in a Nutshell

Statements

A simple statement is an expression evaluated for its side effects. Every simple statement must end in a semicolon, unless it is the final statement in a block.

A sequence of statements that defines a scope is called a block. Generally, a block is delimited by braces, or { }. Compound statements are built out of expressions and blocks. A conditional expression is evaluated to determine whether a statement block will be executed. Compound statements are defined in terms of blocks, not statements, which means that braces are required.

Any block can be given a label. Labels are identifiers that follow the variable-naming rules (i.e., they begin with a letter or underscore, and can contain alphanumerics and underscores). They are placed just before the block and are followed by a colon, like SOMELABEL here:

SOMELABEL: {
  ...statements...
  }

By convention, labels are all uppercase, so as not to conflict with reserved words. Labels are used with the loop-control commands next, last, and redo to alter the flow of execution in your programs.

Conditionals and Loops

The if and unless statements execute blocks of code depending on whether a condition is met. These statements take the following forms:

if (expression) {block} else {block}

unless (expression) {block} else {block}

if (expression1) {block}
elsif (expression2) {block}
  ...
elsif (lastexpression) {block}
else {block}

while loops

The while statement repeatedly executes a block as long as its conditional expression is ...

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Publisher Resources

ISBN: 1565922867Catalog PageErrata