$value1 = "a";
$value2 = "b";
$value3 = "c";
$value4 = "de";
$value5 = "f";

my $key = join("", $value1,$value2,$value3,$value4,$value5);
print $key;

$value3 = "cd";
$value4 = "e";

$key = join("", $value1,$value2,$value3,$value4,$value5);
print $key;

##</code><code>##

my $str = "v1=$value1,v2=$value2,v3=$value3,v4=$value4,v5=$value5";
# use $str for key, or perhaps generate hash of $str and use that