From: WATANABE Hirofumi <watanabe@...>
Date: 1998-07-06T15:13:05+09:00
Subject: [ruby-dev:3222] Re: [BUG] a ||= 1 and a &&= 1

わたなべです.

Keiju ISHITSUKA <keiju@rational.com> writes:

:しかし, ||=の利用価値は分かりますが, &&= は何か用途が思い浮かばないで
:すよね...

||= は elisp の defvar みたいなもんですね.
&&= は perl でも 1 個所しか見つかりませんでした.
/usr/local/lib/perl5/Exporter.pm:

sub require_version {
    my($self, $wanted) = @_;
    my $pkg = ref $self || $self;
    my $version = ${"${pkg}::VERSION"};
    if (!$version or $version < $wanted) {
	$version ||= "(undef)";
	my $file = $INC{"$pkg.pm"};
	$file &&= " ($file)";
	require Carp;
	Carp::croak("$pkg $wanted required--this is only version $version$file")
    }
    $version;
}