Hello, tybalt89, Thank you so much for your help! How can your code work on my code? Thank you so much! 

open(IN1, "tmp11") || die "Cannot open this file"; 
@lines = <IN1>; 
$i = 0; 

for (@lines) 
  { 
  $lines[$i]=~s/(^| \K)(?!\d)/0/g;; 
  $thislines[$i]=$lines[$i]; 
  print $thislines[$i]; 
  $i++;
  } 

open(OUT, ">tmp12") || die "Cannot open this file";

for $thisline(@thislines)
  { 
  print OUT $thisline;
  } 

close(OUT); 
close(IN1);
1    2            2        5                4
4    4    4            4                3    
        4    4            1                
    1    5    6        4

[download]

It will come out 

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

[download]

2018-08-19 Athanasius restored content

In reply to Re^3: substitute space to 0 by yueli711
in thread substitute space to 0 by yueli711

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