$Max = $ARGV[3]; #no $Pad needed. And I added $Max
until ( $Start > $Max ) { 
  print "$Pre$Start$Post\n";
  getstore ( 
        $Url, 
        "$Start$Post"
       );
  $Start = substr(++($Start="z$Start"),1);
}
# or see it work with this one-liner...
perl -e '$a="0035";until($a>50){print$a=substr(++($a="z$a"),1),$/}'