use strict;
use warnings;

my @nos = qw{
   12304500
   123
   1234567000000
   987045027000
};

print
   map { sprintf qq{%15s : %5s\n}, @$_ }
   map { [ $_, m{(\d{1,5})(?=0*\z)} ] }
   @nos;

##</code><code>##

       12304500 : 23045
            123 :   123
  1234567000000 : 34567
   987045027000 : 45027