use strict ;
use warnings ;

my @addresses = qw(you@somewhere.com
                   me@here
		   me@here@there@everywhere
                   why@
		   @.it) ;

foreach (@addresses) {
  print "$_ is " ;
  print /^\S+\@([a-z-]+\.)+[a-z]{2,4}$/ ? "GOOD!!!" : "bad" ;
  print "\n" ;
}

##</code><code>##

you@somewhere.com is GOOD!!!
me@here is bad
me@here@there@everywhere is bad
why@ is bad
@.it is bad