Hello, tybalt89, Thank you so much for your great help.

The data file is 

1    2            2        5                4
4    4    4            4                3    
        4    4            1                
    1    5    6        4

[download]

It comes out 


1    2            2        5                4
4    4    4            4                3    
0        4    4            1                
0    1    5    6        4                    



#!/usr/bin/perl

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

use strict;
use warnings;


open(DATA,"DATA")||die"cannot open the file: $!\n";


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

[download]

In reply to Re^2: substitute space to 0 by yueli711
in thread substitute space to 0 by yueli711

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