I suppose you didn't write what you thought you were writing. First, square brackets are not used to make a list, like in python, but an arrayref, which is only one element. So @a contains only one element which is [1,2,3]. @b on the other is indeed an array.

Could you write what you were intending to in python? If I translate your code it would be something like: 

for each element in @b
   $a[1] = element
   print $a[1]
done

[download]

If you want to use the indexes in @a to go through @b you can either use a slice (EDIT: not splice ...) of @b : 

@a = (1,2,3);
@b = (2,4,6,7);
print for @b[@a]; # print for elements of @b with indexes in @a

[download]
Or loop through @a : 
@a = (1,2,3);
@b = (2,4,6,7);
for $i (@a)
{
   print $b[$i];
}

[download]

NB: As for the error, I guess in for VAR (LIST) VAR can only be a variable, not any lvalue.

In reply to Re: Using an array element as a loop iterator by Eily
in thread Using an array element as a loop iterator by gurpreetsingh13

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.