#!/usr/bin/perl
use strict;
use warnings;

while (<DATA>) {
	s[^\s*\S+\K(.*)$][$1 =~ tr/ \t/,/rs]e;
	print;
}

__DATA__
I like  this     script
     I like   this script


##</code><code>##

I,like,this,script
     I,like,this,script