Editing Perl module (section)

===Packages and modules===
Conventionally, namespaces are associated with modules; in practice, there is usually one namespace per module and vice versa, but that's not mandated by the language. For example, the 'standard' module CGI.pm has the following declaration at its top:
<syntaxhighlight lang="perl">
package CGI;
</syntaxhighlight>
This module, and its functionality, would commonly be invoked as follows:
<syntaxhighlight lang="perl">
use CGI (':standard'); # imports many functions, including b()
...
print b('Hello, world'); # outputs <b>Hello, world</b>
</syntaxhighlight>
A 'missing' subroutine ''could'' be added from the using program's namespace.
<syntaxhighlight lang="perl">
sub CGI::bi { # define target namespace (CGI) and sub name (bi)
    return b(i($_[0]));
}
</syntaxhighlight>
and invoked as below:
<syntaxhighlight lang="perl">
print CGI::bi('Hello, world'); # outputs <b><i>Hello, world</i></b>
</syntaxhighlight>
However, though technically feasible, that would be dubious programming practice. You might just as well define the sub in the calling namespace, and call it from that namespace.