If you're talking about dynamically choosing the target of the link in response to another action on the page, you can't do it in perl. You can only target links on the client side: the server doesn't know anything about your frames or their relations. It just sends back the page it's asked for, and the browser takes care of displaying it in the right place. You'd need some javascript.

But just in case you're talking about the point where you return the page containing the link, as the $cust in your snippet suggests, then here's one of the approximately 17,354 ways to do it:

my $target = ($use_foo) ? 'foo' : 'bar';
print qq|<a href="..." target="$target"> $cust</a>|;
[download]

you'll find many more in perlsyn.

my($url1, $url2, $url3);
$url1 = "$ENV{'SCRIPT_NAME'}\??item\&$kb\&$kc";
$url2 = "http://blah";
$url3 = "http://blah2";

if($foo1){
   &update_frame($url1);
}
elsif($foo2){
   &update_frame($url2);
}
else{
   &update_frame($url3);
}

sub update_frame{
   my($url) = $_[0];
   print <<HTML;

    <script language = 'JavaScript'>
    <!--
    parent.info.location = "$url";
    //-->
    </script>;
    
    HTML
}
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Under normal cicumstances that would always refresh the page on which the link is clicked, which isn't really ideal. What you really want is to mimic normal browser behaviour but with server-side flexibility and control.

but it occurs to me that this could be a good solution if combined with a very small, preferably blank, routing frame. All links should be target="trampoline" and the very small, quick page returned to the trampoline frame could force the selected content frame to refresh.

but op would still be using two or more cgi calls, as well as the javascript, where one at most should do it. it's going to be slow and ungainly and have way too many points of possible failure.

/will can't remember the last time frames seemed like a good idea, but thinks netscape 2 was still a novelty at the time...

Please, can you explain with more details your problem?