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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" -> "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
require 5.002;
require Exporter;
@ISA = qw(Exporter);
@EXPORT = qw(gensym ungensym qualify);
my $genpkg = "Symbol::";
my $genseq = 0;
my %global;
while (<DATA>) {
chomp;
$global{$_} = 1;
}
sub gensym () {
my $name = "GEN" . $genseq++;
local *{$genpkg . $name};
\delete ${$genpkg}{$name};
}
sub ungensym ($) {}
sub qualify ($;$) {
my ($name) = @_;
if (! ref($name) && $name !~ /::/) {
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;
__DATA__
ARGV
ARGVOUT
ENV
INC
SIG
STDERR
STDIN
STDOUT
|
