my %seen;
open(FILE, '<', 'file.txt') or die "Unable to open file.txt for reading, $!";
while (<FILE>) {
  chomp;
  tr/0-9//cd;

if (length $_ >=7 && length $_ <= 10)
{
  $_ = sprintf("%010s", $_);
  $_ =~ s/(\d{3})(\d{3})(\d{4})/$1-$2-$3/;
  $seen{$_}++;
}