A simple JSONP wrapper with Perl

#!"\xampp\perl\bin\perl.exe"
#
#  jsonp.pl
#
#  Reads a json file and wraps it in a JavaScript function call
#  One reason to do this is for better decoupling: A JSON file on the server contains the data
#  But the Javascript function to be applied on it belongs to the Web UI (i.e. to the HTML/CSS/JS layer)
#
#  With the HTML element
#    <script src="status.js?jsonp=show_status"></script>
#  the server will send back: "show_status( <content of status.js> );"
#
#  Thus, the UI-specific function show_status will immediately be executed on receive
#
#  Combine this with an internal redirection of query strings in your server
#  In Apache, you may write in your .htaccess
#
#     RewriteEngine on
#     RewriteCond %{QUERY_STRING}     jsonp=([^&]*)                       [NC]
#     RewriteRule ^(.*)$              /cgi-bin/jsonp.pl?file=$1&jsonp=%1  [PT,L]
#

use strict;
use warnings;

my %args = ();
foreach (split /&/, $ENV{QUERY_STRING}) {
  my ($name,$value) = split /=/;
  $args{$name} = $value;
  }

print "Content-type: text/javascript; charset=utf-8\n\n";

if (not exists $args{file}) {
  print "Error: No JSON file given in URL path\n";
  exit;
}

if (not exists $args{jsonp}) {
  print "Error: No 'jsonp' parameter specified\n";
  exit;
}

open( my $JSON,"<$ENV{DOCUMENT_ROOT}/$args{file}");
if (not $JSON) {
  print "Can't open '$args{file}': $!";
  exit;
}

print "$args{jsonp}(\n";
foreach (<$JSON>) {
  print;
}
print "\n);";

close $JSON;