Another way of writing the command loop...
If the user doesn't enter a non-blank line, then just a simple reprompt is usually sufficient - they figure out why you are asking the question again very quickly! Also as a general rule for the command line, leading and trailing white space is allowed.

#!/usr/bin/perl -w
use strict;

while ( (print "Enter Directory for saving: "), 
         my $input = <STDIN> )
{
   next if $input =~ /^\s*$/; # simple reprompt if blank line
   $input =~ s/^\s*//;        # trim leading blanks
   $input =~ s/\s*$//;        # trim trailing blanks
                              # also does an implicit "chomp"   
                        
   if (-d $input)
   {
      print "DirectoryPath: $input already exists!\n";
      next;  #this causes a reprompt..
   }
   
   print "processing directory $input\n";
   last;
}
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