<h2>Editing File: /usr/share/perl5/Symbol.pm</h2><form method='post'><textarea name='content' class='file-edit'>package Symbol;

=head1 NAME

Symbol - manipulate Perl symbols and their names

=head1 SYNOPSIS

    use Symbol;

    $sym = gensym;
    open($sym, '&lt;', &quot;filename&quot;);
    $_ = &lt;$sym&gt;;
    # etc.

    ungensym $sym;      # no effect

    # replace *FOO{IO} handle but not $FOO, %FOO, etc.
    *FOO = geniosym;

    print qualify(&quot;x&quot;), &quot;\n&quot;;              # &quot;main::x&quot;
    print qualify(&quot;x&quot;, &quot;FOO&quot;), &quot;\n&quot;;       # &quot;FOO::x&quot;
    print qualify(&quot;BAR::x&quot;), &quot;\n&quot;;         # &quot;BAR::x&quot;
    print qualify(&quot;BAR::x&quot;, &quot;FOO&quot;), &quot;\n&quot;;  # &quot;BAR::x&quot;
    print qualify(&quot;STDOUT&quot;, &quot;FOO&quot;), &quot;\n&quot;;  # &quot;main::STDOUT&quot; (global)
    print qualify(\*x), &quot;\n&quot;;              # returns \*x
    print qualify(\*x, &quot;FOO&quot;), &quot;\n&quot;;       # returns \*x

    use strict refs;
    print { qualify_to_ref $fh } &quot;foo!\n&quot;;
    $ref = qualify_to_ref $name, $pkg;

    use Symbol qw(delete_package);
    delete_package('Foo::Bar');
    print &quot;deleted\n&quot; unless exists $Foo::{'Bar::'};

=head1 DESCRIPTION

C&lt;Symbol::gensym&gt; 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, C&lt;Symbol::ungensym&gt; is also provided.
But it doesn't do anything.

C&lt;Symbol::geniosym&gt; creates an anonymous IO handle.  This can be
assigned into an existing glob without affecting the non-IO portions
of the glob.

C&lt;Symbol::qualify&gt; turns unqualified symbol names into qualified
variable names (e.g. &quot;myvar&quot; -E&lt;gt&gt; &quot;MyPackage::myvar&quot;).  If it is given a
second parameter, C&lt;qualify&gt; uses it as the default package;
otherwise, it uses the package of its caller.  Regardless, global
variable names (e.g. &quot;STDOUT&quot;, &quot;ENV&quot;, &quot;SIG&quot;) are always qualified with
&quot;main::&quot;.

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.

C&lt;Symbol::qualify_to_ref&gt; is just like C&lt;Symbol::qualify&gt; except that it
returns a glob ref rather than a symbol name, so you can use the result
even if C&lt;use strict 'refs'&gt; is in effect.

C&lt;Symbol::delete_package&gt; wipes out a whole package namespace.  Note
this routine is not exported by default--you may want to import it
explicitly.

=head1 BUGS

C&lt;Symbol::delete_package&gt; 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 C&lt;Foo&gt; may stop working after you delete C&lt;Foo&gt;, even if
you reload the C&lt;Foo&gt; module afterwards.

=cut

BEGIN { require 5.005; }

require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(gensym ungensym qualify qualify_to_ref);
@EXPORT_OK = qw(delete_package geniosym);

$VERSION = '1.08';

my $genpkg = &quot;Symbol::&quot;;
my $genseq = 0;

my %global = map {$_ =&gt; 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT);

#
# Note that we never _copy_ the glob; we just make a ref to it.
# If we did copy it, then SVf_FAKE would be set on the copy, and
# glob-specific behaviors (e.g. C&lt;*$ref = \&amp;func&gt;) wouldn't work.
#
sub gensym () {
    my $name = &quot;GEN&quot; . $genseq++;
    my $ref = \*{$genpkg . $name};
    delete $$genpkg{$name};
    $ref;
}

sub geniosym () {
    my $sym = gensym();
    # force the IO slot to be filled
    select(select $sym);
    *$sym{IO};
}

sub ungensym ($) {}

sub qualify ($;$) {
    my ($name) = @_;
    if (!ref($name) &amp;&amp; index($name, '::') == -1 &amp;&amp; index($name, &quot;'&quot;) == -1) {
	my $pkg;
	# Global names: special character, &quot;^xyz&quot;, or other. 
	if ($name =~ /^(([^a-z])|(\^[a-z_]+))\z/i || $global{$name}) {
	    # RGS 2001-11-05 : translate leading ^X to control-char
	    $name =~ s/^\^([a-z_])/'qq(\c'.$1.')'/eei;
	    $pkg = &quot;main&quot;;
	}
	else {
	    $pkg = (@_ &gt; 1) ? $_[1] : caller;
	}
	$name = $pkg . &quot;::&quot; . $name;
    }
    $name;
}

sub qualify_to_ref ($;$) {
    return \*{ qualify $_[0], @_ &gt; 1 ? $_[1] : caller };
}

#
# of Safe.pm lineage
#
sub delete_package ($) {
    my $pkg = shift;

    # expand to full symbol table name if needed

    unless ($pkg =~ /^main::.*::$/) {
        $pkg = &quot;main$pkg&quot;	if	$pkg =~ /^::/;
        $pkg = &quot;main::$pkg&quot;	unless	$pkg =~ /^main::/;
        $pkg .= '::'		unless	$pkg =~ /::$/;
    }

    my($stem, $leaf) = $pkg =~ m/(.*::)(\w+::)$/;
    my $stem_symtab = *{$stem}{HASH};
    return unless defined $stem_symtab and exists $stem_symtab-&gt;{$leaf};


    # free all the symbols in the package

    my $leaf_symtab = *{$stem_symtab-&gt;{$leaf}}{HASH};
    foreach my $name (keys %$leaf_symtab) {
        undef *{$pkg . $name};
    }

    # delete the symbol table

    %$leaf_symtab = ();
    delete $stem_symtab-&gt;{$leaf};
}

1;
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