when used in scalar context, readdir returns undef when there are no more entries:

opendir DIR, q{.} or die $!,$/;
my $last;
while (my $file = readdir DIR) {
   $last = $file;
}
print $last; ## this prints the last file
closedir DIR;
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OTOH, if you use readdir in list context, it will return you a null list when no entries are available.

opendir DIR, q{.} or die $!,$/;
my @files = readdir DIR;
closedir DIR;
print $files[-1];  ## this prints the last file
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## sorted by name, case sensitive
my @files = sort {$a cmp $b} readdir DIR;
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Given the fact that a directory handle is a typeglob (approximately) and recursion is always with us, I find the best way to do readdirs is "all at once", this reduces the chance that I will have two directory handles with the same name interfere with each other.

{
  my(@files,$file);
  local(*DIR);

  opendir(DIR,$dir_name);
  @files = readdir(DIR);
  closedir(DIR);

  foreach $file (@files)
    {
      next if(/^\.\.?/);
      ...
    }
}
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If you adopt this strategy then your question becomes "how do I find out if this item is last one on the list", and therefore very easy to answer.

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

opendir( DIR, './' );
my @files = readdir( DIR );
closedir( DIR );

my $i = scalar @files;

foreach my $file ( @files )
{
    $i--;

    # do something with the items in list

    if ( $i == 0 )
    {
        # do something special with last one.
    }
}
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Wonko

Well, after

opendir( DIR, './' );
my @files = readdir( DIR );
closedir( DIR );
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you can get the last element with my $last = $files[-1];Hardly a good golfer, just an avid reader of perldata ;-)