This chapter is a quick and merciless guide to the
Perl language itself.
If you're trying to learn Perl from
scratch, and you'd prefer to be taught rather than to have things
thrown at you, then you might be better off with
by Randal Schwartz and Tom Christiansen, or
on Win32 Systems
by Randal Schwartz, Erik Olson, and Tom Christiansen.
However, if you already know some other programming languages
and just want to hear the particulars of Perl, this chapter
is for you. Sit tight, and forgive us for being terse: we have
a lot of ground to cover.
If you want a more complete discussion of the Perl language
and its idiosyncrasies (and we mean
Wall, Tom Christiansen, and Randal Schwartz.
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 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.
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.
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.
command-line switch will warn
you about using undefined values.
You may force yourself to declare your variables
by including the
pragma in your programs (see
, for more information on pragmas and
in particular). This
makes it an error to not explicitly declare your variables.
Comments and documentation
Comments within a program are indicated by a pound sign (
following a pound sign to the end of the line is interpreted as a comment.
Lines starting with
are interpreted as the start
of a section of embedded documentation (pod), and all
subsequent lines until the next
are ignored by the
Section 4.11, "Pod
" later in this
chapter for more information on pod format.
Copyright © 2001 O'Reilly & Associates. All rights reserved.