Testing for a '\' in a string

[Bret Goodfellow]

Hi all,
 
I am trying to evaluate a string, and determine if the last charater of
the string has a backslash '\' .  The piece of code I am using doesn't
appear to work.  What I've found with this peice of code is that if the
string does contain a \, then the following code still adds another
slash.  If there is not backslash in the string, the the code appears to
work fine by adding a backslash.  Any ideas?
 
   print "Deleting old directory $dir_no: $Dir_name\n";
   $arg_length = length($ARGV[0]);
   $arg_lastchar = substr($ARGV[0], $arg_length-1, 1);
   print "last char is: $arg_lastchar\n";
   ################################################
   # add a \ if one was not present in argument   #
   ################################################
if ($arg_lastchar ne '\\' or $arg_lastchar ne '/') {
    $Dir_name = '\\' . $Dir_name;
    print "Adding \\ to: $Dir_name\n";
   }