In the docs example, it is implicitly looping over $_ in the line for (0 .. $max). In your case you are using $i (which is probably a good thing), so you should use that instead: $next_update = $progress->update($i) if $i >= $next_update.

Yes that did it. I still don't for the life of me see where $_ is getting updated in the sample code. Isn't $i the index in the sample? Maybe it's some Perl voodoo/arcana I don't understand.

I ... don't ... see where $_ is getting updated in the sample code.

In a Perl-style for-loop like
    for (0 .. $max) { ... }
the scalar variable $_ is the implicit loop or "topicalized" variable. (Update: See Foreach Loops in perlsyn.)

---

Give a man a fish:  <%-{-{-{-<

G'day cormanaz,

"I don't understand what is setting $_ ..."

In the examples in the "module docs", $_ is being set in the outer loop and $i is being set in the inner loop. A quick demonstration:

$ perl -E '
    for ("a" .. "b") {
        for my $i (1 .. 2) {
            say "\$_[$_] \$i[$i]";
        }
    }
'
$_[a] $i[1]
$_[a] $i[2]
$_[b] $i[1]
$_[b] $i[2]
[download]

Using a named variable, as you've done, is much safer. $_ is a global variable: it could be changed by something in "stuff my script is actually processing"; or, some later addition to your code could affect it.

$ perl -E '
    for my $f ("a" .. "b") {
        for my $i (1 .. 2) {
            say "\$_[$_] \$f[$f] \$i[$i]";
        }
    }
'
$_[] $f[a] $i[1]
$_[] $f[a] $i[2]
$_[] $f[b] $i[1]
$_[] $f[b] $i[2]
[download]

Here's a highly contrived example of additional code changing $_:

$ perl -E '
    for my $f ("a" .. "b") {
        for my $i (1 .. 2) {
            say "\$_[$_] \$f[$f] \$i[$i]";
        }
        s/$/.bu/;
    }
'
$_[] $f[a] $i[1]
$_[] $f[a] $i[2]
$_[.bu] $f[b] $i[1]
$_[.bu] $f[b] $i[2]
[download]

If you'd put "use warnings;" near the top of your code, you would have seen a series of "Use of uninitialized value $_ ..." warnings. This may have alerted you to the problem you describe.

While I appreciate that the code you provided was purely for demo purposes, I thought I'd point out that "my $max = $f;" is going to be a problem with real filenames (you may already be aware of this). You get no output from:

$ perl -E '
    for my $f ("a" .. "b") {
        my $max = $f;

        for my $i (1 .. $max) {
            say "\$f[$f] \$i[$i]";
        }
    }
'
[download]

Again, the warnings pragma points to the problem:

$ perl -E '
    use warnings;

    for my $f ("a" .. "b") {
        my $max = $f;

        for my $i (1 .. $max) {
            say "\$f[$f] \$i[$i]";
        }
    }
'
Argument "a" isn't numeric in foreach loop entry at -e line 7.
Argument "b" isn't numeric in foreach loop entry at -e line 7.
[download]

I strongly recommend that you include the warnings pragma in all of your code. It's lexically scoped: turn off selected warnings, in a limited scope, for special cases.

$ perl -E '
    use warnings;

    my @rgb = qw{#ff0000 #00ff00 #0000ff};
'
Possible attempt to put comments in qw() list at -e line 4.

$ perl -E '
    use warnings;

    my @rgb;
    {
        no warnings "qw";
        @rgb = qw{#ff0000 #00ff00 #0000ff};
    }
'
[download]