#!/usr/bin/perl -T  

use warnings;
use strict;

use CGI;
use JSON;

my $q = CGI->new;

my @pars = $q->params;

my $wordref =  decode_json($pars[0]);

my $word =  $wordref->{word} ;

#untaint word

die "invalid input" unless $word =~ /^([\w\s]+)$/;

$word = $1;

... # mess about with db and/or word;

$wordref->{word} = $word;

my $jsonobj = encode_json($wordref);