What I think is confusing you is at what point $x is getting initialized. Becuse you do not explicitly intialize it it does not get set to 0 on the first iteration. Try the code: 
 #!/usr/bin/perl
foo();
bar();
for (1..3) {
    my $x=0;
    sub foo { print ++$x }
    sub bar { print ++$x }
    print ++$x;
}

[download]
With this code you get the more expected output of 12111.

If seems that perl is "optimizing" your loop in some very odd manner.

It may be (I did not look a the perl source) that perl is unrolling the loop so that it ends up looking something like: 

foo();
bar();
{
    my $x;
    sub foo { print ++$x; }
    sub bar { print ++$x; }
    print ++$x;
    {
        my $x;
        for (2..3) {
            print ++$x;
            undef $x;
        }
    }
}

[download]
That is: one $x is used for the closure and the first time through the loop and a different $x is used for the other times throught the loop.

Update: updated the code of the second fragment to make it more clear what I think perl is doing. Added some text as well.

-- gam3
A picture is worth a thousand words, but takes 200K.

In reply to Re: Trying to understand closures by gam3
in thread Trying to understand closures by shine22vn

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