my @fieldNames=
    qw( MemoryLoad TotalPhys AvailPhys TotalPageFile
        AvailPageFile TotalVirtual AvailVirtual );
my %unitSize= ( B=>1, K=>1024, M=>1024*1024, G=>1024*1024*1024 );
#[...]
    my( $sUnits )= "B";
    if(  @_  &&  $_[0] =~ /^[BKMG]B?$/i  ) {
        $sUnits= uc substr(shift(@_),0,1);
    }
    my( $nUnits )= $unitSize{$sUnits};
    my( $dwMSLength )= 0;
    my( @fieldValues )= (0)x@fieldNames;
    my $MEMORYSTATUS= pack "L8", $dwMSLength, @fieldValues;
    $GlobalMemoryStatus->Call($MEMORYSTATUS);
    ( $dwMSLength, @fieldValues )=
        unpack "L8", $MEMORYSTATUS;
    return   if  0 == $dwMSLength;
    for(  @fieldValues  ) {
        $_ /= $nUnits;
    }
    my $hFields= {};
    @$hFields{@fieldNames}= @fieldValues;
    return @_ ? @$hFields{@_} : $hFields;