#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11148743
use warnings;
use CGI::Tiny;

our $cgi;

cgi {
    $cgi = $_;
    some_sub_somewhere_else();
};

sub some_sub_somewhere_else
  {
  my $bookparam = $cgi->param('book') || '';
  $cgi->render (text => "bookparam is $bookparam\n");
  }