No, no optimization was involved. Don't confuse my $x with undef $x. my $x does NOT change the value of $x. Aside from returning $x's value, all my $x does is set a flag to clear $x at the end of the current scope (i.e. at the end of the loop pass).

Can you guess what the following snippet prints? 

for (1..4) {
   my $x;
   print ++$x;
}

print "\n";

for (1..4) {
   goto SKIP if $_ == 2;
   my $y;
SKIP:
   print ++$y;
}

print "\n";

for (1..4) {
   my $z if $_ != 2;
   print ++$z;
}

[download]

At the end of every pass of the first loop, $x gets cleared, so the output of that loop is 1111.

At the end of every pass *except the second* of the second loop, $y gets cleared, so the output of that loop is 1121.

The third loop is identical to the second one. It also outputs 1121.

Updated: Reworded for clarity. No new content.
Updated: Added code.

In reply to Re^2: Trying to understand closures by ikegami
in thread Trying to understand closures by shine22vn

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