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). 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.
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