@id =<ID_LIST>;
chomp(@id);
while($data = <DB>) {
  chomp($data);  
  foreach $id (@id) {
    if ($data =~ /$id/) {
    print OUT "$data\n";
    }
  }
}


__comment__
sample contents of the ID_LIST:
user45-16.dept12
user35-18.dept19
user05-14.dept10

sample contents of the DB: (3 MB of text)
home--user45-16.dept12-ph#435
home66--user05-17.dept19-ddfg#5;v6.0234
home4--user35-18.dept19-hj#5
home87--user05-14.dept10-dfg#7;v2.0