#!perl
use strict;
use warnings;
use feature 'experimental::signatures';
use Memoize;

my @values = (0,0,0,1,2,3,4,5,10,101,102,103);
my $MIN = 1;
my $MAX = 10;

# this is the slow part:
sub get_element_value( $index ) {
    sleep 1;
    return $values[$index]
};

# Cache indices that we have fetched once already
memoize 'get_element_value';

sub get_index_of_element_larger_than( $value, $low, $high ) {
    my $next_try = int(($low+$high) / 2);
    my $v = get_element_value( $next_try );
    if( $v > $value ) {
        return get_index_of_element_larger_than( $low, $next_try-1 );
    } else {
        return get_index_of_element_larger_than( $next_try+1, $high );
    }
}