man Symbol () - manipulate Perl symbols and their names
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
CWSymbol::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, CWSymbol::ungensym is also provided. But it doesn't do anything.
CWSymbol::geniosym creates an anonymous IO handle. This can be assigned into an existing glob without affecting the non-IO portions of the glob.
CWSymbol::qualify turns unqualified symbol names into qualified variable names (e.g. myvar -> MyPackage::myvar). If it is given a second parameter, CWqualify 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.
CWSymbol::qualify_to_ref is just like CWSymbol::qualify except that it returns a glob ref rather than a symbol name, so you can use the result even if CWuse strict 'refs' is in effect.
CWSymbol::delete_package wipes out a whole package namespace. Note this routine is not exported by defaultyou may want to import it explicitly.
BUGS
CWSymbol::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 CWFoo may stop working after you delete CWFoo, even if you reload the CWFoo module afterwards.