How did you learn about mkdir? By reading perlfunc right? If you read closely you'll notice what I've hilighted

mkdir FILENAME,MASK
mkdir FILENAME
Creates the directory specified by FILENAME, with permissions specified by MASK (as modified by "umask"). If it succeeds it returns true, otherwise it returns false and sets $! (errno). If omitted, MASK defaults to 0777.

In general, it is better to create directories with permissive MASK, and let the user modify that with their "umask", than it is to supply a restrictive MASK and give the user no way to be more permissive. The exceptions to this rule are when the file or directory should be kept private (mail files, for instance). The perlfunc(1) entry on "umask" discusses the choice of MASK in more detail...

So what are you gonna do next?