Are you sure you want to do

/^(\d+).*/
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If I understand your name construction properly you expected NNNN.NNNN.jpg

I would write the code slightly more carefully (your 1st foreach loop) note the \.

my %uniquelist;
my %deletelist;
my $h = 0;
foreach my $pic (@filelist) {
  next unless ($pic =~ /\.jpg$/);
  if( $pic =~ /^(\d+)\.(\d+)/) {
    my ($num,$counter) = ( $1,$2);
    $h++;
    $uniquelist{$num}++;
    next if ($currentlist{$num});
    $deletelist{$pic}++;
  } else { 
   print STDERR "saw a photo file ($pic) that did not match the expect
+ed naming pattern!\n";
  }
}
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Code suggestion, you might want to replace my $k = 0 + keys %uniquelist; with my $k = scalar keys %uniquelist;, as some may feel this is more explicit.