use warnings;
use strict;

my @data = qw(
    21112340    21112341    21112342    21112343
    21112344    21112345    21112346    21112347
    21112348    21112349    21112350    21112351
);

my %sixpack;

for my $item (@data) {
    my $suffix = chop($item);
    $sixpack{$item}{$suffix}++;
}

for my $six (sort keys %sixpack) {
    if (scalar(keys %{$sixpack{$six}}) == 10) {
        print "$six\n";
    }
    else {
        print "$six$_\n" for sort keys %{$sixpack{$six}};
    }
}

#!/usr/bin/perl
use strict;
use warnings;

my @array=(
    21112340,
    21112341,
    21112342,
    21112343,
    21112344,
    21112345,
    21112346,
    21112347,
    21112348,
    21112349,
    21112350,
    21112351,
  );
my %test;
for(@array)
{ $test{$1}+=2**$2 if($_=~/^(\d{7})(\d)/); }

my @new_array;
for my $val (@array)
{
  my $v=substr($val,0,7);
  if($test{$v} && $test{$v}==(2**10)-1)
  { push(@new_array,$v) if(!@new_array or $new_array[-1]!=$v); }
  else
  { push(@new_array,$val) }
}

print "$_\n" for(@new_array);

#!/usr/bin/perl
use strict;
use 5.010;
use warnings;

my @aa = qw /
21112340
21112341
21112342
21112343
21112344
21112345
21112346
21112347
21112348
21112349
21112350
21112351
/;

my (%za, @new);

# präfixe zählen, zehner  speichern
for ( @aa ) {

  /^\d{7}/;

  $za{$&}++;

  push @new, $& if ($za{$&} == 10)

}

# speichern alles was < 10 ist
for ( @aa ) { 

  /^\d{7}/;

  push @new, $_ if ( $za{$&} < 10 )
  
}

print "$_\n" for( @new ) # noch sortieren