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# Symbol

Perl 5 version 22.0 documentation
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# Symbol

- NAME
- SYNOPSIS
- DESCRIPTION
- BUGS

# NAME

Symbol - 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";              # "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.

Page index

- NAME
- SYNOPSIS
- DESCRIPTION
- BUGS