use strict;
use Win32::OLE('in');
use constant wbemFlagReturnImmediately => 0x10;
use constant wbemFlagForwardOnly => 0x20;

my $flashdriveletter;
my $flashdrivename = 'foo';
my $computer = ".";
my $objWMIService = Win32::OLE->GetObject("winmgmts:\\\\$computer\\root\\CIMV2") or die "WMI connection failed.\n";
my $colItems = $objWMIService->ExecQuery("SELECT * FROM Win32_LogicalDisk","WQL",wbemFlagReturnImmediately | wbemFlagForwardOnly);

foreach my $objItem (in $colItems) {
    if ( $objItem->{VolumeName} eq /$flashdrivename/ ) {
        $flashdriveletter = $objItem->{Caption};
    }
}