


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";              # "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).



perl v5.10.1                2009-10-12                          1





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


       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 v5.10.1                2009-10-12                          2


