Do you know what  @foo = $bar does?

Let's try it

#!/usr/bin/perl --
use strict;
use warnings;
use Data::Dump qw/ dd pp /;
my @foo = 1..3;
dd\@foo;
@foo = 7..9;
dd\@foo;
@foo = 4;
dd\@foo;
@foo = 2;
dd\@foo;
@foo = ( 4, @foo );
dd\@foo;
__END__
[1, 2, 3]
[7, 8, 9]
[4]
[2]
[4, 2]
[download]

Do you get the problem now ?

perlintro#Arrays shows/links some interesting functions like reverse, and http://perldoc.perl.org/index-functions-by-cat.html#Functions-for-real-@ARRAYs lists some more, as do various Tutorials/manuals in Data Type: Array

$ perl beans
Global symbol "$index" requires explicit package name at beans line 11
+.
Execution of beans aborted due to compilation errors.
[download]

Whoops, looks like you need to clean your room better :)