Programming Perl, 4th Edition

Compound Statements

A sequence of statements within a scope^[69] is called a block. Sometimes the scope is the entire file, such as a required file or the file containing your main program. Sometimes the scope is a string being evaluated with eval. But, generally, a block is surrounded by braces ({}). When we say scope, we mean any of these three. When we mean a block with braces, we’ll use the term BLOCK.

Compound statements are built out of expressions and BLOCKs. Expressions are built out of terms and operators. In our syntax descriptions, we’ll use the word EXPR to indicate a place where you can use any scalar expression. To indicate an expression evaluated in list context, we’ll say LIST.

The following statements may be used to control conditional and repeated execution of BLOCKs. (The LABEL portion is optional.)

if (EXPR) BLOCK
if (EXPR) BLOCK else BLOCK
if (EXPR) BLOCK elsif (EXPR) BLOCK ...
if (EXPR) BLOCK elsif (EXPR) BLOCK ... else BLOCK

unless (EXPR) BLOCK
unless (EXPR) BLOCK else BLOCK
unless (EXPR) BLOCK elsif (EXPR) BLOCK ...
unless (EXPR) BLOCK elsif (EXPR) BLOCK ... else BLOCK

given (EXPR) BLOCK

LABEL while (EXPR) BLOCK
LABEL while (EXPR) BLOCK continue BLOCK

LABEL until (EXPR) BLOCK
LABEL until (EXPR) BLOCK continue BLOCK

LABEL for (EXPR; EXPR; EXPR) BLOCK

LABEL foreach (LIST) BLOCK
LABEL foreach (LIST) BLOCK continue BLOCK
LABEL foreach VAR (LIST) BLOCK
LABEL foreach VAR (LIST) BLOCK continue BLOCK

LABEL BLOCK
LABEL BLOCK continue BLOCK

Note that unlike in C and Java, ...