Symbol(3p) Perl Programmers Reference Guide Symbol(3p)NAMESymbol - manipulate Perl symbols and their names
SYNOPSIS
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 Symbolqw(delete_package);
delete_package('Foo::Bar');
print "deleted\n" unless exists $Foo::{'Bar::'};
DESCRIPTION
"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 quali-
fied 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::".
perl v5.8.8 2005-02-05 1
Symbol(3p) Perl Programmers Reference Guide Symbol(3p)
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.
perl v5.8.8 2005-02-05 2
