use strict;
use warnings;

my ($ex, $ex1, $ex2, @test);
my $length = 14;

for $ex1 (1..15) {
    for $ex2 (5..15) {
        push @test, 'a' x $ex1 . '@' . 'b' x $ex2;
    }
}

for (@test, <DATA>) {
    chomp;
    if (length($_) > $length) {
        $ex = length($_) - $length + 3;
        @_ = split /@/;
        if (length($_[1]) > $ex) {
            substr($_[1], length($_[1]) - $ex, $ex) = '...';
        }
        else {
            $ex += 3;
            $ex2 = length($_[1]) - 1;
            $ex1 = $ex - $ex2;
            if ($ex1 < 4) {
                $ex1 = 4;
                $ex2 = $ex - $ex1;
            }
            substr($_[0], length($_[0]) - $ex1, $ex1) = '...';
            substr($_[1], length($_[1]) - $ex2, $ex2) = '...';
        }
        $_ = join '@', @_;
    }
    print "$_\n";
}

__DATA__
ted@dingos.com
mary@supercalifradulistic.org
i.am.a.purple.dinosaur@barney.must.die.com