search(simple => $stuff);

search(normal => $stuff);

search(extended => $stuff);

##</code><code>##

use Carp;

sub search($$) {
     my(%parameter);  # Those parameters that you set
     my $mode = shift;
     if($mode eq 'simple') {
         # set parameters to simple
           ...
     } elsif($mode eq 'normal') {
         # set parameters to normal
           ...
     } elsif($mode eq 'extended') {
         # set parameters to extended
           ...
     } else {
         croak("mode '$mode' not supported");
     }

     # Now just do your process_search
        ...
}