LWP::SimpleでHEAD

use LWP::Simple;

my $url = 'http://www.example.com/';
my ( $content_type, $document_length, $modified_time, $expires, $server ) = head( $url );
# or
my $head = head( $url );
print $head->{_headers}->{etag};
print $head->{_headers}->{'last-modified'};