CHIPS / perl5.003_11 / lib / Symbol.pm 

            

              
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package Symbol;
=head1 NAME
Symbol - manipulate Perl symbols and their names
=head1 SYNOPSIS
    use Symbol;
    $sym = gensym;
    open($sym, "filename");
    $_ = <$sym>;
    # etc.
    ungensym $sym;      # no effect
    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
=head1 DESCRIPTION
C<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, C<Symbol::ungensym> is also provided.
But it doesn't do anything.
C<Symbol::qualify> turns unqualified symbol names into qualified
variable names (e.g. "myvar" -E<gt> "MyPackage::myvar").  If it is given a
second parameter, C<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 qualfied 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.
=cut
BEGIN { require 5.002; }
require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(gensym ungensym qualify);
my $genpkg = "Symbol::";
my $genseq = 0;
my %global = map {$_ => 1} qw(ARGV ARGVOUT ENV INC SIG STDERR STDIN STDOUT);
sub gensym () {
    my $name = "GEN" . $genseq++;
    local *{$genpkg . $name};
    \delete ${$genpkg}{$name};
}
sub ungensym ($) {}
sub qualify ($;$) {
    my ($name) = @_;
    if (!ref($name) && index($name, '::') == -1 && index($name, "'") == -1) {
        my $pkg;
        # Global names: special character, "^x", or other. 
        if ($name =~ /^([^a-z])|(\^[a-z])$/i || $global{$name}) {
            $pkg = "main";
        }
        else {
            $pkg = (@_ > 1) ? $_[1] : caller;
        }
        $name = $pkg . "::" . $name;
    }
    $name;
}
1;