use File::Spec;

# define variables as above

opendir(CURRDIR, $mypath) or die "Can't open $mypath: $!";
my @files = map { File::Spec->catfile($mypath, $_) }
	    grep { /^[\d\w\s]+\.$filetype/ }
	    readdir CURRDIR;

foreach my $file (@files) {
	# reveal potentially nasty leading/trailing whitespace
	print "Processing ->$file<-\n";
	my $book = $Excel->Workbooks->Open($file) 
		or die "Error opening $file: $!";
	$book->Close();
}