DB<98> say "$_:\t", $_ =~ s/(\w\w).*\@.*(\.\w*)/$1...\@...$2/r for qw/someone@example.co.uk andrew.test@some.company.co.uk jo@abc.com/

someone@example.co.uk:  so...@....uk
andrew.test@some.company.co.uk: an...@....uk
jo@abc.com:     jo...@....com

##</code><code>##

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