use strict;
use warnings;

$_ = q{aaa@z.com bbb@z.com ccc@z.com};
print qq{$_\n};

s{([^@]+@)[^.]+}{${1}something}g;
print qq{$_\n};

##</code><code>##

aaa@z.com bbb@z.com ccc@z.com
aaa@something.com bbb@something.com ccc@something.com