for ( @array ) {
    if ( exists $hash{$_} ) {
        # do something
    } else {
        # do something else
    }
}

##</code><code>##

@array = sort @array;
foreach ( keys %hash ) {
    if ( is_in_array( $_ ) ) {
       # do something
    } else {
       # do something else
    }
}