1.3 Namespaces
A
namespace
is implemented as a table containing the names of the variables and
subroutines in a program. The table itself is called a
symbol table and is used by the running program to
keep track of variable values and subroutine definitions as the
program evolves. A namespace and a symbol table are essentially the
same thing. A namespace exists under the hood for many programs,
especially those in which only one default namespace is used.Large programs often accidentally use the same variable name for
different variables in different parts of the program. These
identically named variables may unintentionally interact with each
other and cause serious, hard-to-find errors. This situation is
called namespace
collision. Separate namespaces are one way to
avoid namespace collision.The package declaration described in the next
section is one way to assign separate namespaces to different parts
of your code. It gives strong protection against accidentally using a
variable name that's used in another part of the
program and having the two identically-named variables interact in
unwanted ways.
1.3.1 Namespaces Compared with Scoping: my and use strict
The unintentional interaction between variables with the same name is
enough of a problem that Perl provides more than one way to avoid it.
You are probably already familiar with the use of
my to
restrict the scope of a variable to its enclosing block (between
matching curly braces {}) and should be accustomed to
using the directive use strict
to require the use of my for all variables.
use strict and my are a great
way to protect your program from unintentional reuse of variable
names. Make a habit of using my and working under
use strict. |
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