... snippet ...
# here, you untainted the argv[1], but not the hash value!
if ($argv[1] =~ /^(.+\@.+\..+)$/) {
    $argv[1] = $1;

    say "Looking while Untainted...";
    say "EMAIL: $argv[1]";
    say __LINE__, ": argv is ", (tainted($argv[1])?'':'not ', "tainted");

    # edit: uncomment here to untaint the hash value as well
    #$data{'email'} = $argv[1];
}
say "argv is ", (tainted($argv[1])?'':'not ', "tainted");
say "data{email} is ", tainted($data{'email'})?'':'not ', "tainted";
... snippet ...
__END__