#!/usr/bin/env perl 
use strict;
use warnings;
use Time::Piece;

my @lines = (
qq{Misc data that is unimportant:false,true,false,"retrieved_on":1433507459,more misc data,nul;,true,"created_utc":"1433122764",\n},
qq{"retrieved_on":1433507472,misc data,"created_utc":"1433122764",true,false,more misc data\n}
);

foreach (@lines) {
    $_ =~ s/([\d]{10})/(localtime $1)->datetime/eg;
    print;
}