#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11132285
use warnings;

my @email = (
    'someone@example.co.uk',
    'andrew.test@some.company.co.uk',
    'jo@abc.com',
);

foreach my $em(@email) 
  {
  print "$em - ";
  $em =~ s/\w{2}\K(\w*)/ $1 =~ tr!!.!cr /ge;
  print "$em\n";
  }

##</code><code>##

someone@example.co.uk - so.....@ex......co.uk
andrew.test@some.company.co.uk - an.....te..@so...co......co.uk
jo@abc.com - jo@ab..co.