title: Why does concatenation of strings with escaped characters work differently in this Perl example?
body: <p>there: 
  I'm new to Perl, and get a string concatenation problem of it. I have two strings below:</p>
  
  <pre><code>my $string1 = "hello\U\Q \t\n\f\b\aWorld" . "\n" . "\E";
  my $string2 = "hello\U\Q \t\n\f\b\aWorld\n\E";
  </code></pre>
  
  <p>They are looked the same to me, until i print them out. 
  <code>$string1</code> looks like this:</p>
  
  <pre><code>hello\ \    \
  \
   \WORLD
  </code></pre>
  
  <p>and with a bell ring.</p>
  
  <p><code>$string2</code> is this one:</p>
  
  <pre><code>hello\ \    \
  \
   \WORLD\
  </code></pre>
  
  <p>with the same bell ring, and a backslash at the tail.</p>
  
  <p>Why does <code>$string2</code> get a backslash at its end but <code>$string1</code> doesn't?</p>