Well, first you need to open the file. Then call a split and assign the hash accordingligly. Here goes (it's untested, but it should work):

$IN = '/path/to/file';
open IN;
while(<IN>) {
    next if /^$/;
    ($key,$value) = split /\s*:\s*/;
    $hash{uc $key} = $value;
}
[download]

If you wish to store multiple names in the same hash, however(for example, the file has many Contact_Names, you need to devise a better way, and need to decide what you want to sort by. One option would be to store on Contact_Name, assuming they are all unique. You could then make the contact_name key point to a reference to a hash, which would store the rest of the information. There are *many* different ways to do this and go about it, but it all depends on the data you are expecting.