For all exercises: no fork/exec/system/qx/open, no cmdline options,
  no user input, no modules, no tie, no bless, no %SIG.  Make sure you
  don't depend on random factors, such as exact values of addresses.
  All solutions should be executable from the cmdline using perl -e

For extra points, try to make them work under strict
  (warning: for one exercise no strict solution is known (yet))
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Exercise 1:  Create an array @x such that changing $x[0] also sets
    $x[1] to the same value

Exercise 2:  Given a pre-declared function "foo", write a code snippet
    that invokes it in an infinite loop; in 10 chars

Exercise 3a: Create $foo such that \$foo->[1] == \$foo->{1}
Exercise 3b: Create $foo such that \$foo->[1] == \$foo->(1)
    You must use different solutions for the two

Exercise 4:  Dump core in 6 chars

Exercise 5:  Create a static variable lexically scoped to a sub, and
    no wider than that.  It's ok if it blows up under recursion

Exercise 6:  Create $x, $y such that $x eq $y && $$x ne $$y

Exercise 7:  Create $foo such that fileno($foo) && !*$foo

Exercise 8:  Create $foo such that ($foo^=0)++ eq $foo++

Exercise 9a: Create $foo such that eval(q[$$foo]) != eval(q[0+$$foo])
Exercise 9b: Create $foo such that eval(q[$$foo =~ / /]) && !$$foo

Exercise 10: Make $x::y::x::y::y::x::y::x::x::y::y::y::y::x::y::y true
    in 26 chars of code

Exercise 11: Make <STDOUT> eq <+STDOUT> in 25 chars

Bonus Exercise:  The code snippet 'sub foo{} goto +foo' produces an
    error: "Can't find label SCALAR(0x31c70c)"  (the address may vary)
    Where does that ref come from?  What does it point to?
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Please black-box solutions/spoilers so people can safely read discussion without seeing all the answers. (for example use: <table bgcolor="#00000000"><tr><td><font color="#00000000">Text goes here</font></table>)

UPDATE: clarification of exercise 5: "static variable" means a variable whose value is retained across multiple invocations of the sub (like static vars in C), and being "scoped to a sub and no wider" means that the standard solution { my $x; sub { ... } } doesn't qualify, because $x is one block wider than the sub. (it is static though)
UPDATE: minor reformatting to make everything fit in 70 columns
UPDATE: they're designed for 5.8, though most probably have solutions on older versions too.