use strict;
use warnings;

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

foreach my $em(@email) {
	print "$em - ";

	my ($name, $comp) = split /@/, $em;
	$em =~ /^(\w[\w|\.]).*@(\w\w).*\.(\w+)$/;
	$em = $1 . '.' x (length($name) - 2) . "\@$2" . '.' x (length($comp) - length($3) - 2) . $3;

	print "$em\n";
}

##</code><code>##

C:\Users\joolz\Perl>perl regtest.pl
someone@example.co.uk - so.....@ex.........uk
andrew.test@some.company.co.uk - an.........@so..............uk
jo@abc.com - jo@ab..com