Program Structure
Perl is a particularly forgiving language, as far as program layout goes. There are no rules about indentation, newlines, etc. Most lines end with semicolons, but not everything has to. Most things don’t have to be declared, except for a couple of things that do. Here are the bare essentials:
- Whitespace
Whitespace is required only between items that would otherwise be confused as a single term. All types of whitespace—spaces, tabs, newlines, etc.—are equivalent in this context. A comment counts as whitespace. Different types of whitespace are distinguishable within quoted strings, formats, and certain line-oriented forms of quoting. For example, in a quoted string, a newline, a space, and a tab are interpreted as unique characters.
- Semicolons
Every simple statement must end with a semicolon. Compound statements contain brace-delimited blocks of other statements and do not require terminating semicolons after the ending brace. A final simple statement in a block also does not require a semicolon.
- Declarations
Only subroutines and report formats need to be explicitly declared. All other user-created objects are automatically created with a null or 0 value unless they are defined by some explicit operation such as assignment. The -w command-line switch will warn you about using undefined values.
You may force yourself to declare your variables by including the
use strictpragma in your programs (see Chapter 8 for more information on pragmas andstrictin particular). This ...