my $possible_file = shift;
 
my $found_file = find_file($possible_file);

{
	local *INPUT;
	open(INPUT, $found_file) or die "Can't open $found_file: $!";
	my $line = <INPUT>;
	# do something with $line
	close INPUT or die "Can't close $found_file.  Bogosity: $!";
}

sub find_file {
	my $file = shift;
	while (-d $file) {
		# the next line may differ on Win/Mac/Un*x
		my @files = glob("$possible_file/*.*");
		foreach (@files) {
			find_file($_);
		}
		# we're not dealing with a file anymore, so return
	}
	return $file;
}