Perl 5 version 8.9 documentation
Declares the compilation unit as being in the given namespace. The scope of the package declaration is from the declaration itself through the end of the enclosing block, file, or eval (the same as the
myoperator). All further unqualified dynamic identifiers will be in this namespace. A package statement affects only dynamic variables--including those you've used
localon--but not lexical variables, which are created with
my. Typically it would be the first declaration in a file to be included by the
useoperator. You can switch into a package in more than one place; it merely influences which symbol table is used by the compiler for the rest of that block. You can refer to variables and filehandles in other packages by prefixing the identifier with the package name and a double colon:
$Package::Variable. If the package name is null, the
mainpackage as assumed. That is,
$::sailis equivalent to
$main::sail(as well as to
$main'sail, still seen in older code).
If NAMESPACE is omitted, then there is no current package, and all identifiers must be fully qualified or lexicals. However, you are strongly advised not to make use of this feature. Its use can cause unexpected behaviour, even crashing some versions of Perl. It is deprecated, and will be removed from a future release.