Is share agent?

gistfile1.pl

sub is_share_agent {
	my $self  = shift;
	
	my $ua    = $self->req->headers->user_agent;
	my $range = $self->req->headers->header('Range');
	my $enc   = $self->req->headers->header('Accept-Encoding');
	
	return
		$ua =~ /facebookexternalhit/ &&  $range &&  $enc eq 'gzip' ? 'facebook'  :
		$ua eq 'Mozilla'             && !$range &&  $enc eq 'gzip' ? 'buzz'      :
		$ua =~ /Mozilla/             &&  $range && !$enc           ? 'vkontakte' :
		undef
	;
}