Here's what I came up with after some reworking. I decided to go with a hash reference as the main parameter instead of taking words. This also means that it must now be called like this:

my %hMem = (TotalPhys =>0, AvailPhys =>0);
Win32::MemoryInfo::MemoryStatus(%hMem,"MB");
[download]

I don't know what the consensus is on putting values into a hash like that, but if someone doesn't check the return value at least they won't get bit with undef values.
Here's the reworked function:

sub MemoryStatus (\%;$) {
   my $return = shift;
   my $ret_type = shift;
   my %fmt_types = 
   ( B => 1, KB => 1024, MB => 1024*1024, GB => 1024*1024*1024);
   my @params = qw(MemLoad TotalPhys AvailPhys TotalPage
                   AvailPage TotalVirtual AvailVirtual);
   my %results;
   my $MemFormat;
   my $dwMSLength;

   $MemFormat = 
   ($ret_type =~ /^[BKMG]B?$/) ? $fmt_types{$ret_type} : $fmt_types{B}
+;

   my $GlobalMemoryStatus ||= 
   new Win32::API("kernel32", "GlobalMemoryStatus", ["P"], "V") or ret
+urn undef;
   
   my $MEMORYSTATUS = pack "L8",(0, 0, 0, 0, 0, 0, 0, 0);

   $GlobalMemoryStatus->Call($MEMORYSTATUS);
   
   ($dwMSLength, @results{@params})  =
   unpack "L8", $MEMORYSTATUS;
   return undef if ($dwMSLength == 0);

   if (keys(%$return) == 0) {
   foreach (@params) {
    $return->{$_} = ($_ eq "MemLoad") ? $results{$_} : $results{$_}/$M
+emFormat;
    }
   }
   else {
    foreach (@params){
     $return->{$_} = $results{$_}/$MemFormat unless (!defined($return-
+>{$_}));
     }
   }
1;
}
[download]

Guildenstern
Negaterd character class uber alles!