#!/usr/bin/perl
use warnings;
use strict;
use CGI qw/:standard/;
use File::Replace qw/replace3/;
use JSON::PP qw/encode_json decode_json/;

# NOT RECOMMENDED, use an alternative like Mojo instead!

my $DATA_FILE = '/path/to/data.json';

my $defaults = decode_json( do { open my $fh, '<', $DATA_FILE
	or die "$DATA_FILE: $!"; local $/; <$fh> } );

print header;

print start_html('Hello, World!');

if ( param('Submit') ) {
	my (undef,$outfh,$repl) = replace3($DATA_FILE);
	print $outfh encode_json {
		name => scalar param('name'),
	};
	$repl->finish;
	print p( "Form submitted!" );
}

print start_form;
print div( label({-for=>'name'}, "Your Name"),
	textfield('name', $defaults->{name}) );
print div( submit('Submit') );
print end_form;

print p( a({-href=>url(-absolute=>1)}, 'Reset') );

print end_html;