use strict;
use warnings;

{
	my $str = "/rootdir/sub1/sub2/sub3/sub4/";
	print substr($str, 0, rindex($str, "/", length($str) - 2));
}
print "\n";
{
	my $str = "/rootdir/sub1/sub2/sub3/sub4";
	print substr($str, 0, rindex($str, "/", length($str) - 2));
}