#!/usr/bin/perl 

# https://perlmonks.org/?node_id=1220510 

open(IN1, "tmp01") || die "Cannot open this file"; 
@lines = <IN1>; 

use strict; 
use warnings; 

while( <IN1> ) 
  { 
  s/(^| \K)(?!\d)/0/g; 
  print; 
  }