NAME
Symbol - manipulate Perl symbols and their names
SYNOPSIS
print ${*{Symbol::fetch_glob("$class\::VERSION")}};
*{Symbol::fetch_glob("foo") = sub { "this is foo" };
keys %{Symbol::stash("main")};
use Symbol;
$sym = gensym;
open($sym, "filename");
$_ = <$sym>;
# etc.
ungensym $sym; # no effect
# replace *FOO{IO} handle but not $FOO, %FOO, etc.
*FOO = geniosym;
print qualify("x"), "\n"; # "Test::x"
print qualify("x", "FOO"), "\n" # "FOO::x"
print qualify("BAR::x"), "\n"; # "BAR::x"
print qualify("BAR::x", "FOO"), "\n"; # "BAR::x"
print qualify("STDOUT", "FOO"), "\n"; # "main::STDOUT" (global)
print qualify(\*x), "\n"; # returns \*x
print qualify(\*x, "FOO"), "\n"; # returns \*x
use strict refs;
print { qualify_to_ref $fh } "foo!\n";
$ref = qualify_to_ref $name, $pkg;
use Symbol qw(delete_package);
delete_package('Foo::Bar');
print "deleted\n" unless exists $Foo::{'Bar::'};
DESCRIPTION
Symbol::fetch_glob
returns a reference to the glob for the specified symbol name. If the symbol does not already exists it will be created. If the symbol name is unqualified it will be looked up in the calling package.
Symbol::stash
returns a refernce to the stash for the specified name. If the stash does not already exists it will be created. The name of the stash does not include the "::" at the end.
Symbol::gensym
creates an anonymous glob and returns a reference to it. Such a glob reference can be used as a file or directory handle.
For backward compatibility with older implementations that didn't support anonymous globs, Symbol::ungensym
is also provided. But it doesn't do anything.
Symbol::geniosym
creates an anonymous IO handle. This can be assigned into an existing glob without affecting the non-IO portions of the glob.
Symbol::qualify
turns unqualified symbol names into qualified variable names (e.g. "myvar" -> "MyPackage::myvar"). If it is given a second parameter, qualify
uses it as the default package; otherwise, it uses the package of its caller. Regardless, global variable names (e.g. "STDOUT", "ENV", "SIG") are always qualified with "main::".
Qualification applies only to symbol names (strings). References are left unchanged under the assumption that they are glob references, which are qualified by their nature.
Symbol::qualify_to_ref
is just like Symbol::qualify
except that it returns a glob ref rather than a symbol name, so you can use the result even if use strict 'refs'
is in effect.
Symbol::delete_package
wipes out a whole package namespace. Note this routine is not exported by default--you may want to import it explicitly.
BUGS
Symbol::delete_package
is a bit too powerful. It undefines every symbol that lives in the specified package. Since perl, for performance reasons, does not perform a symbol table lookup each time a function is called or a global variable is accessed, some code that has already been loaded and that makes use of symbols in package Foo
may stop working after you delete Foo
, even if you reload the Foo
module afterwards.