title: What does s/\G /0/g mean?
body: <p>I'm using regex in Perl. One of the things I've come across:</p>
  
  <pre><code>my $n = "   49 here";
  $n =~ s/\G /0/g;
  print $n;
  </code></pre>
  
  <p>This gives:</p>
  
  <pre><code>00049 here
  </code></pre>
  
  <p>I know the <code>s</code> modifier (single-line). I also understand the <code>g</code> modifier (global, which keeps track of the last match position). I know the regex replaces something with zeros but I don't understand what the <code>\G</code> AND the whitespace following it do (without the whitespace following <code>\G</code> the result is: <code>0  49 here</code>).</p>