1Symbol(3pm)            Perl Programmers Reference Guide            Symbol(3pm)
2
3
4

NAME

6       Symbol - manipulate Perl symbols and their names
7

SYNOPSIS

9           use Symbol;
10
11           $sym = gensym;
12           open($sym, "filename");
13           $_ = <$sym>;
14           # etc.
15
16           ungensym $sym;      # no effect
17
18           # replace *FOO{IO} handle but not $FOO, %FOO, etc.
19           *FOO = geniosym;
20
21           print qualify("x"), "\n";              # "main::x"
22           print qualify("x", "FOO"), "\n";       # "FOO::x"
23           print qualify("BAR::x"), "\n";         # "BAR::x"
24           print qualify("BAR::x", "FOO"), "\n";  # "BAR::x"
25           print qualify("STDOUT", "FOO"), "\n";  # "main::STDOUT" (global)
26           print qualify(\*x), "\n";              # returns \*x
27           print qualify(\*x, "FOO"), "\n";       # returns \*x
28
29           use strict refs;
30           print { qualify_to_ref $fh } "foo!\n";
31           $ref = qualify_to_ref $name, $pkg;
32
33           use Symbol qw(delete_package);
34           delete_package('Foo::Bar');
35           print "deleted\n" unless exists $Foo::{'Bar::'};
36

DESCRIPTION

38       "Symbol::gensym" creates an anonymous glob and returns a reference to
39       it.  Such a glob reference can be used as a file or directory handle.
40
41       For backward compatibility with older implementations that didn't
42       support anonymous globs, "Symbol::ungensym" is also provided.  But it
43       doesn't do anything.
44
45       "Symbol::geniosym" creates an anonymous IO handle.  This can be
46       assigned into an existing glob without affecting the non-IO portions of
47       the glob.
48
49       "Symbol::qualify" turns unqualified symbol names into qualified
50       variable names (e.g. "myvar" -> "MyPackage::myvar").  If it is given a
51       second parameter, "qualify" uses it as the default package; otherwise,
52       it uses the package of its caller.  Regardless, global variable names
53       (e.g. "STDOUT", "ENV", "SIG") are always qualified with "main::".
54
55       Qualification applies only to symbol names (strings).  References are
56       left unchanged under the assumption that they are glob references,
57       which are qualified by their nature.
58
59       "Symbol::qualify_to_ref" is just like "Symbol::qualify" except that it
60       returns a glob ref rather than a symbol name, so you can use the result
61       even if "use strict 'refs'" is in effect.
62
63       "Symbol::delete_package" wipes out a whole package namespace.  Note
64       this routine is not exported by default--you may want to import it
65       explicitly.
66

BUGS

68       "Symbol::delete_package" is a bit too powerful. It undefines every
69       symbol that lives in the specified package. Since perl, for performance
70       reasons, does not perform a symbol table lookup each time a function is
71       called or a global variable is accessed, some code that has already
72       been loaded and that makes use of symbols in package "Foo" may stop
73       working after you delete "Foo", even if you reload the "Foo" module
74       afterwards.
75
76
77
78perl v5.10.1                      2009-02-25                       Symbol(3pm)
Impressum