Symbol

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



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 sup-
       port 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 vari-
       able 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 perfor-
       mance 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			  2001-09-21			    Symbol(3)