[1] perlvar - search.cpan.org (2/26/2015, 10:34:25 AM 版) <http://search.cpan.org/dist/perl/pod/perlvar.pod#Error_Variables>
[2] perlvar - search.cpan.org (2/26/2015, 10:34:25 AM 版) <http://search.cpan.org/dist/perl/pod/perlvar.pod#$!>
Google search: $!