use CGI;
use HTML:Template;
# .. then initialise $q and get input so we know what to do

sub Send_Header {
    my $header_tmpl = HTML::Template->new(
        filename => 'header.tmpl'
    );
    $header_tmpl->param(
        header => shift,
        to => shift,
        date => substr(scalar gmtime time, 0, 10),
        subject => shift,
    ); 
    print $header_tmpl->output();
}

print $q->header();
print $q->start_html(
    -title => $title,
    -style => {'src' => '../styles/main.css'},
);
Send_Header($header,$user,$subject)
# rest of message goes here