$ cat test2.pl 
#!/usr/bin/perl -w

my $d1 = "d1";
my $d2 = "d2";

mkdir "/tmp/$d1/$d2" or warn __LINE__ . " mkdir /tmp/$d1/$d2 failed:$!\n";
mkdir "/tmp/$d1" or warn __LINE__ . " mkdir /tmp/$d1 failed:$!\n";
mkdir "/tmp/$d1/$d2" or warn __LINE__ . " mkdir /tmp/$d1/$d2 failed:$!\n";
$ ./test2.pl 
6 mkdir /tmp/d1/d2 failed:No such file or directory