use strict;
use warnings 'all';

my $found;

for my $in_path (@INC){
	next if ! -e $in_path."\\Win32API\\File.pm";
	print "found module in $in_path ...\n";
	$found = 1; 
	last;
}

if ($found){
	require 'Win32API::File';
	my @drv = map{s/\\$//;lc}  
               Win32API::File::getLogicalDrives();
	print @drv;
}

##</code><code>##

H:\>perl testINC.pl
found module in C:/Perl/site/lib ...
Can't locate Win32API::File in @INC (@INC contains: C:/Perl/lib C:/Perl/site/lib .) at testINC.pl line 14.