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Symbol - manipulate Perl symbols and their names
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::'};
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.
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.