my $saw_alpha = 0;
my $saw_charlie = 0;
while( <DAT> ) {
    if( /alpha/ ) {
        ++$saw_alpha;
        last if $saw_charlie;
    }
    if( /charlie/ ) {
        ++$saw_charlie;
        last if $saw_alpha;
    }
}
++$lacking_both unless $saw_alpha and $saw_charlie;

##</code><code>##

   push @lacking_both, $name