You just need to capture the output of the regexp match, which Perl makes available in $1.

See Extracting matches.

(Update: added link to docs)

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

my $book= "^\\s\*book ref \#";
my $book_res = $book =~ "/^\\s\*owner \#/";

my $title = "^\\s\*title ";
my $title_res = $title =~ "/^\\s\*title /";

my %keepers;

foreach (<DATA>) {
  #next unless /$book|$title/ip;
  chomp;

  if ( /($book|$title)/ip ) {
    $keepers{ $_ } = $1;
  }
   #print ;
}

# here i would like to access the regex matches as scalers

for (keys %keepers ) {
  print "Here's your scalar: <<$_>> has value <<$keepers{ $_ }>>\n";
}

__DATA__

Book ref #4346
Lent: Sun Jul 12 03:26:43 BST 2015
status Lent
Description: classic
title blah blah blah
last used: 2
color red
Pages 238
Publisher Bca
Type Hardback
Location: N/a
Author R jones
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