use CGI;
my $cgi=CGI->new;
print $cgi->header;
print $cgi->start_html;
my $link=$cgi->param("link");
print "<a href=\"$link\">Link</a><br/>\n";      # BAD!
print "<a href=\"".$cgi->escapeHTML($link)      # Good
            ."\">Link</a><br/>\n";
print $cgi->a({href=>$link},"Link"), $cgi->br;  # Better
print $cgi->end_html;