$ perl -Mstrict -Mwarnings -E '
    my @email = (
        q{someone@example.co.uk},
        q{andrew.test@some.company.co.uk},
        q{jo@abc.com},
    );

    for my $email (@email) {
        my ($nm0, $nm1, $at, $ad0, $ad1, $tld)
            = $email =~ /^(..)([^@]*)(@)(..)(.*?)(\.[^.]+)$/;
        say $email;
        say $nm0, "."x length($nm1), $at, $ad0, "."x length($ad1), $tld;
    }
'
someone@example.co.uk
so.....@ex.........uk
andrew.test@some.company.co.uk
an.........@so..............uk
jo@abc.com
jo@ab..com