my $js = q~
function checkAll(field)
{
        for(i=0;i<field.length; i++)
        field[i].checked=true;
}

function uncheckAll(field)
{
        for(i=0;i<field.length;i++)
        field[i].checked=false;
}


~;

[...]

print $cgi->start_form({-name=>'form1',-action => "/pfad/script.pl", -method=>'post'});
        
        
print $cgi->start_table({-bordercolor=>'#cccccc', -bgcolor=>'#ffffff', -border=>'0', -width=>'700'});
while ($prepare_select_hosts->fetch()){

        print $cgi->Tr(
                        $cgi->td({-width=>'20'},$id),
                        $cgi->td($hostname),
                        $cgi->td($ip),
                        $cgi->td($cgi->checkbox(-name=>'host', -label=>'', -value=>"$ip"))
                );
        }
print $cgi->Tr(
                $cgi->td({-colspan=>'3'},

                $cgi->button(-name=>'checkall',
                             -value=>'Check All',
                             -onMouseOver =>"this.style.color = '#FF0000'",
                             -onMouseOut => "this.style.color = '#000000'",
                             -onClick=>"checkAll(document.form1.host);"),
                
                $cgi->button(-name=>'uncheckall',
                             -value=>'Uncheck All',
                             -onMouseOver =>"this.style.color = '#FF0000'",
                             -onMouseOut => "this.style.color = '#000000'",
                             -onClick=>"uncheckAll(document.form1.host);"),

                        ));
print $cgi->end_table();
print $cgi->end_form();

[...]