MirOS Manual: Symbol(3p)


Symbol(3p)      Perl Programmers Reference Guide       Symbol(3p)

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";              # "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::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

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