(fastolfe) gemina:~$ cat test
use File::Basename;

fileparse_set_fstype('MSWin32');   # Because I'm on Unix

while (<DATA>) {
        chomp;
        printf("%20s %s\n", $_, basename($_));
}

__DATA__
a:\pic3.jpg
a:\some\dir\pic.jpg
a:\some\other\pic
\blah\pic.
a:\pic
a:pic.jpg
a:\pic3.

(fastolfe) gemina:~$ perl test
         a:\pic3.jpg pic3.jpg
 a:\some\dir\pic.jpg pic.jpg
   a:\some\other\pic pic
          \blah\pic. pic.
              a:\pic pic
           a:pic.jpg pic.jpg
            a:\pic3. pic3.
[download]

So if File::Basename is working properly, perhaps your input is messed up somehow? Are you reading your filenames from a file perhaps and forgetting to chop off the newline?