You have provided your variables as stringified hash keys as well as test variables and then you're testing their existence against hash values, but $hash{'s'} and $hash{'p1'} values are "empty" still the tests results are not consistent, condsider:

if ( $s =~ $$hash{ "s" }) 
     { print "\t1 ok\n";}else { print "\t1 NOK\n";

if ($d =~ $$hash{ "p1" }){ print "\t2 ok\n";}else{ print "\t2 NOK\n";}
!
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and you get back:

1 ok #is returned even when the hash doesn't have a corresponding valu
+e for $s.
3 NOK #this works correct for $p1?
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Since you have used strings, you better use the string comparison operator "eq" and not the =~, and I bet you got tired of the excessive concatenation, use ' ' around the hash keys instead of " " and you would've been saved the trouble...

#!/usr/local/bin/perl
#title "Multiple Test Regex Does not work the way I expect";
#see the '' around hash keys..

$hash = {
"s" => "",
"d" => "19.28.18.28",
"p1" => "",
"p2" => "88"
};

$s="192.168.3.79";
$d="19.28.18.28";
$p1="3269";
$p2="88";


print "$s -> $$hash{'s'}\n";
if ( $s eq $$hash{ "s" }) {
        print "\t1 ok\n";
        }else {
                print "\t1 NOK\n";
                }

print "$d -> $$hash{'d'}\n";
if ($d eq $$hash{ "d" }){
         print "\t2 ok\n";
                }else{
                         print "\t2 NOK\n";
                         }

print "$p1 -> $$hash{'p1'}\n";
if ($p1 eq $$hash{ "p1"}){
        print "\t3 ok\n";
                }else{
                        print "\t3 NOK\n";
                        }

print "$p2 -> $$hash{'p2'}\n";
if($p2 eq $$hash{ "p2" }) {
         print "\t4 ok\n";
                }else {
                         print "\t4 NOK\n";
                         }
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