use strict;
use warnings;

my @chapters          = ( 15, 24, 23, 110, 30, 58, 3, 22, 79, 6 );
my $base              = 1;
my %sentenceToChapter =
   map {
           my $chapter = $_;
           my @range   = ( $base .. $base + $chapters[ $chapter ] - 1 );
           $base       += scalar @range;
           map { $_ => $chapter + 1 } @range;
       }
   0 .. $#chapters;

print qq{Sentence $_ is in chapter $sentenceToChapter{ $_ }\n}
   for qw{ 250 15 16 98 };

##</code><code>##

Sentence 250 is in chapter 6
Sentence 15 is in chapter 1
Sentence 16 is in chapter 2
Sentence 98 is in chapter 4