#!/usr/bin/perl
use strict;
use warnings;

my @array = 1 .. 3_141_592;

for (1 .. 400) {
    my $idx = bin_search(\@array, int(rand 3_141_592) + 1);
}


sub bin_search {
    my ($list, $tgt) = @_;

    return 0       if $tgt < $list->[0];
    return $#$list if $tgt > $list->[-1]; 

    my ($beg, $end, $val) = (0, $#$list, undef);
    while ($beg <= $end) {
        my $mid = int(($beg + $end) / 2);
        $val = $list->[$mid];
        if ($val > $tgt) {
            $end = $mid - 1;
        }
        elsif ($val < $tgt) {
            $beg = $mid + 1;
        }
        else {
            return $mid;
        }        
    }
    return -1;
}