Ilya Zakharevich


Symbol - manipulate Perl symbols and their names


    use Symbol;

    $sym = gensym;
    open($sym, "filename");
    $_ = <$sym>;
    # etc.

    ungensym $sym;      # no effect

    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);
    print "deleted\n" unless exists $Foo::{'Bar::'};


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::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 qualfied 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.

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