use strict ;
use warnings ;
use Win32::Process::Info ;
use Data::Dumper;

foreach ( (Win32::Process::Info->new( '', 'NT' )->GetProcInfo ) ) {
    print Dumper($_);
    print '*'x75, "\n";
}
[download]

The output looked like this (these are the last few):

[...]
$VAR1 = {
          '_status' => 127,
          'ProcessId' => 10524
        };
**********************************************************************
+*****
$VAR1 = {
          '_status' => 127,
          'ProcessId' => 7768
        };
**********************************************************************
+*****
$VAR1 = {
          'WriteOperationCount' => 0,
          'WriteTransferCount' => 0,
          '_status' => 127,
          'MaximumWorkingSetSize' => 1413120,
          'MinimumWorkingSetSize' => 204800,
          'OtherOperationCount' => 1104,
          'OtherTransferCount' => 9046,
          'CreationDate' => 1530745952,
          'KernelModeTime' => '0.03125',
          'UserModeTime' => '0.15625',
          'ProcessId' => 484,
          'ReadTransferCount' => 398115,
          'ReadOperationCount' => 77
        };
**********************************************************************
+*****
[download]

None of the hashes that were output contained a key called 'Name'. I found if I removed the arguments to Win32::Process::Info->new( '', 'NT' ) that the returned hashes do contain a key called 'Name'.

use strict ;
use warnings ;
use Win32::Process::Info ;
use Data::Dumper;

foreach ( (Win32::Process::Info->new( )->GetProcInfo )[-1]) {
    print Dumper($_);
    print '*'x75, "\n";
}

__END__
$VAR1 = {
          'QuotaPagedPoolUsage' => 123,
          'ParentProcessId' => 7984,
          'ProcessId' => 5568,
          'Caption' => 'perl.exe',
          'OwnerSid' => 'S-1-5-21-3545305261-4160602198-2318032092-100
+1',
          'ExecutablePath' => 'C:\\Strawberry\\perl\\bin\\perl.exe',
          'Status' => undef,
          'Owner' => 'QUEST\\Brent',
          'WindowsVersion' => '6.3.9600',
          'ThreadCount' => 6,
          'WriteTransferCount' => '0',
          'HandleCount' => 151,
          'TerminationDate' => undef,
          'VirtualSize' => '81350656',
          'SessionId' => 2,
          'UserModeTime' => '0.21875',
          'OtherTransferCount' => '136620',
          'OtherOperationCount' => '4717',
          'KernelModeTime' => '0.203125',
          'InstallDate' => undef,
          'PageFaults' => 4153,
          'PeakPageFileUsage' => 8484,
          'Name' => 'perl.exe',
          'PageFileUsage' => 8484,
          'OSCreationClassName' => 'Win32_OperatingSystem',
          'PrivatePageCount' => '8687616',
          'PeakVirtualSize' => '81350656',
          'QuotaPeakNonPagedPoolUsage' => 12,
          'PeakWorkingSetSize' => 15336,
          'OSName' => 'Microsoft Windows 8.1|C:\\Windows|\\Device\\Har
+ddisk0\\Partition4',
          'Priority' => 8,
          'QuotaNonPagedPoolUsage' => 12,
          'MinimumWorkingSetSize' => 200,
          'MaximumWorkingSetSize' => 1380,
          'CSCreationClassName' => 'Win32_ComputerSystem',
          'CSName' => 'QUEST',
          'QuotaPeakPagedPoolUsage' => 123,
          'ReadOperationCount' => '86',
          'Description' => 'perl.exe',
          'Handle' => '5568',
          'WriteOperationCount' => '0',
          'CreationDate' => 1530731971,
          'ExecutionState' => undef,
          'CommandLine' => '"C:\\Strawberry\\perl\\bin\\perl.exe" "C:\
+\usr\\pm\\Win32\\win32processinfo_noargs.pl"  ',
          'ReadTransferCount' => '375821',
          'CreationClassName' => 'Win32_Process',
          'WorkingSetSize' => '15704064'
        };
**********************************************************************
+*****
[download]

I found a description of the arguments to new in the documentation that explains what happens if no arguments are passed to new.

$pi = Win32::Process::Info->new ([machine], [variant], [hash])
This method instantiates a process information object, connected to th
+e given machine, and using the given variant.

The following variants are currently supported:

NT - Uses the NT-native mechanism. Good on any NT, including Windows 2
+000. This variant does not support connecting to another machine, so 
+the 'machine' argument must be an empty string (or undef, if you pref
+er).

PT - Uses Dan Urist's Proc::ProcessTable, making it possible (paradoxi
+cally) to use this module on other operating systems than Windows. On
+ly those Proc::ProcessTable::Process fields which seem to correspond 
+to WMI items are returned. Caveat: the PT variant is to be considered
+ experimental, and may be changed or retracted in future releases.

WMI - Uses the Windows Management Implementation. Good on Win2K, ME, a
+nd possibly others, depending on their vintage and whether WMI has be
+en retrofitted.

The initial default variant comes from environment variable PERL_WIN32
+_PROCESS_INFO_VARIANT. If this is not found, it will be 'WMI,NT,PT', 
+which means to try WMI first, NT if WMI fails, and PT as a last resor
+t. This can be changed using Win32::Process::Info->Set (variant => wh
+atever).
[download]

The WMI variant seems to be providing more information that includes the 'Name' key. I then modified Memory.pm on my machine so that new is called with no arguments. At that point the following test script will just hang.

use strict ;
use warnings ;
use Win32::Process::Memory ;
my $proc = Win32::Process::Memory->new({ name => 'cmd.exe' });
#my $proc = Win32::Process::Memory->new({ name => 'notepad.exe' });
print "ok1\n";
printf "Commited Memory = %X Bytes\n", $proc->get_memtotal ;
print "ok2\n";
__END__
pargs->pid = 7984
hi 1
hi 2
ok1
hi 3
.....(hangs here)
[download]

Here is the part of memory.pm that I added some print statements to for debugging.

    # get process handle by command line name
    if ( defined( $pargs->{name} ) ) {
        eval 'use Win32::Process::Info;';
        die "Win32::Process::Info is required to get process by name" 
+if $@;
        $pargs->{name} = lc( $pargs->{name} );
        #foreach ( Win32::Process::Info->new( '', 'NT' )->GetProcInfo 
+) {
        foreach ( Win32::Process::Info->new(        )->GetProcInfo ) {
            if ( lc( $_->{Name} ) eq $pargs->{name} ) {
                $pargs->{pid} = $_->{ProcessId};
                print "pargs->pid = $pargs->{pid}\n";
                last;
            }
        }
    }

    # get process handle by pid
    if ( defined( $pargs->{pid} ) ) {
        my $hProcess = _OpenByPid( $pargs->{pid}, $access );
        print "hi 1\n";
        $this->{hProcess} = $hProcess if $hProcess;
        print "hi 2\n";
    }

    return $this;
}

sub DESTROY {
    my $this = shift;
    _CloseProcess( $this->{hProcess} ) if defined $this->{hProcess};
}

sub get_memlist { _GetMemoryList( $_[0]->{hProcess} ); }

sub get_memtotal {
    my $this    = shift;
    print "hi 3\n";
    my %memlist = $this->get_memlist;
    print "hi 4\n";
    my $sum     = 0;
    $sum += $_ foreach values %memlist;
    return $sum;
}
[download]