How to start in Perl several other perl scripts?

Just doing my last step at the Exodus from Windows: Rewriting my old MSHTA dependent software to client server.

In the Windows version:
MSIE was used as GUI, *.hta applications, something like html where
<script language=PerlScript>
....here goes all the Perl code
</script>

In the new client server version:
Google Chrome as GUI.
The perl script service.pl opens a port,
starts the browser with http://localhost:10500/here-some-parameters
The perl script is called on port 10500 and delivers the html page.

There is a list of domains, and each domain has links on the page
* to call the CMS for this domain
* to view the local version of the domain

View the local version works fine.
The page javascript calls server.pl with

function view(site)
{
var xhttp = new XMLHttpRequest();
xhttp.open('GET', url+'?do=view&site='+site, true);
xhttp.send();
}

and in server.pl

if ( $do eq 'view' )
{
system ( $wm2::browser, "$path::inteet/$site/index.htm" );
retu;
}

For each click, a new window opens, showing the localc stored start page of the wanted domain.

The problem is opening the CMS for a domain.
The javascript

function wsc(i)
{
var xhttp = new XMLHttpRequest();
xhttp.open('GET', url+'?do=WSC&index='+i, true);
xhttp.send();
}

and in server.pl

if ( $do eq 'WSC' )
{
my $i = $wm2::data_hash { 'index'};
my $site = $site::tab [ $i ];
my $port = 10510 + $i;

system ( "perl", "$path::inteet/cgi.pege.org/cgi-bin/server.pl", "task=WSC", "site=$site", "port=$port" );
retu;
}

A new windows opens with the CMS for the wanted domain,
but after this, no click creates an reaction, the browser window with the domain list is dead.

So I think, calling the browser, the browser retus controll to server.pl after opening a new browser window
but calling perl, the controll is not retued to server.pl, so server.pl can not react any more.

In windows,
system ( "start", "perl.exe", "$path::inteet/cgi.pege.org/cgi-bin/server.pl", "task=WSC", "site=$site", "port=$port" );
helped,
but I can not find out gow to do it here