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32.39. Symbol
use Symbol "delete_package";
delete_package("Foo::Bar");
print "deleted\n" unless exists $Foo::{"Bar::"};
use Symbol "gensym";
$sym1 = getsym();# Returns new, anonymous typeglob.
$sym2 = getsym();# Yet another new, anonymous typeglob.
package Demo;
use Symbol "qualify";
$sym = qualify("x");# "Demo::x"
$sym = qualify("x", "Foo");# "Foo::x"
$sym = qualify("Bar::x");# "Bar::x"
$sym = qualify("Bar::x", "Foo");# "Bar::x"
use Symbol "qualify_to_ref";
sub pass_handle(*) {
my $fh = qualify_to_ref(shift, caller);
...
}
# Now you can call pass_handle with FH, "FH", *FH, or \*FH.
The Symbol module provides functions to help manipulate global
names: typeglobs, format names, filehandles, package symbol tables, and
anything else you might want to name via a symbol table. The
delete_package function completely clears out a package's namespace
(effectively anonymizing any extra references to the symbol table's
referents, including references from precompiled code). The gensym
function returns an anonymous typeglob each time it is called. (This
function isn't used so much these days, now that undefined scalars
autovivify into proper filehandles when used as arguments to open,
pipe, socket, and the like).The qualify function takes a name that may or may not be completely
package-qualified, and returns a name that is. If it needs to prepend
the package name, it will use the name specified via the second argument
(or if omitted, your current package name). The qualify_to_ref
function works similarly, but produces a reference to the typeglob the
symbol would represent. This is important in functions that accept
filehandles, directory handles, or format names as arguments but
don't require these to be passed by reference. For example, functions
prototyped with a typeglob accept any of these forms, but don't
automatically convert barewords to symbol table references. By
converting that argument with qualify_to_ref, you can now use the
supplied handle even with strict refs in effect. You may also
bless it into objectdom, since it's a proper reference.