```{index} single: Symbol ``` # Symbol manipulate Perl symbols and their names ## SYNOPSIS ```perl 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"; # "main::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::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.