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What are Packages in Perl?
The package statement in Perl switches the current naming context to a specified namespace (symbol table). Thus −
- A package is a collection of code which lives in its own namespace.
- A namespace is a named collection of unique variable names (also called a symbol table).
- Namespaces prevent variable name collisions between packages.
- Packages enable the construction of modules which, when used, won't clobber variables and functions outside of the modules's own namespace.
- The package stays in effect until either another package statement is invoked, or until the end of the current block or file.
- You can explicitly refer to variables within a package using the :: package qualifier.
Following is an example having main and Foo packages in a file. Here special variable __PACKAGE__ has been used to print the package name.
Example
#!/usr/bin/perl # This is main package $i = 1; print "Package name : " , __PACKAGE__ , " $i\n"; package Foo; # This is Foo package $i = 10; print "Package name : " , __PACKAGE__ , " $i\n"; package main; # This is again main package $i = 100; print "Package name : " , __PACKAGE__ , " $i\n"; print "Package name : " , __PACKAGE__ , " $Foo::i\n"; 1;
Output
When the above code is executed, it produces the following result −
Package name : main 1 Package name : Foo 10 Package name : main 100 Package name : main 10
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