I have always understood that perl is context driven, and I'm quite happy that the "equals" assignment gets over-loaded depending on context: 
   @a = qw(a b c d e);
   @b = @a;  # @b contains (a b c d e)
   $b = @a;  # $b is 5, as the "=" is overloaded by context

[download]
I was teaching an "Introduction to Perl" course the other day, and one of the students had this code (I've paraphrased, as it were): 
   @a = qw(a b c d e);
   $b = @a[1,3];
   print $b

[download]

Now, My understanding is that the code would print "2", being the number of elements in the array-slice. it prints "d"

Indeed, my slides make the point that @array[$n] is a one-element array, not a scalar, thus $b=@array[$n] will set $b to 1, not the value of the array element ($b=$array[$n])! 
   @a = qw(a b c d e);
   $b = @a[1];
   print $b

[download]
prints "b" 
   @a = qw(a b c d e);
   @b = @a[1];
   $b = @b
   print $b

[download]
prints 1

WTF?

So, I tried forcing a scalar context on the assignement: 

   @a = qw(a b c d e);
   $b = scalar @a[1,3];
   print $b

[download]

.... still prints "d"!

Switch the array-slice around, and we still get the last element in the scalar: 
   @a = qw(a b c d e);
   $b = @a[3,1];
   print $b

[download]

prints "b"

Can someone explain why?


-- Ian Stuart
A man depriving some poor village, somewhere, of a first-class idiot.

In reply to Confused as to why the "casting context" is mis-behaving by kiz

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.