Your problem can be demonstrated by following simple code:

my @subs;
for(my $i=1;$i<=5;$i++){
        push @subs, sub {
                print "i=$i\n";
        };
}
$subs[3]->();

[download]

Inside the sub, $i is evaluated at the time the sub is called in the context/scope of the for-loop which has now terminated, so $i=5+1=6, which is the expected behaviour.

A workaround would be to create a sub via eval which will force it to consider $i's value at the time of the eval. But I am not sure if this is an elegant solution:

my @subs;
for(my $i=1;$i<=5;$i++){
        push @subs, eval <<EOE;
sub {
    print "i=$i\n";
};
EOE
}
$subs[3]->();

[download]

btw, once you sort this out, you should start using arrays instead of ${"xx$i"}!

Update: another solution would be to introduce another variable local to the loop scope and use that:

my @subs;
for(my $i=1;$i<=5;$i++){
        my $j = $i;
        push @subs, sub {
          print "i=$i, j=$j\n";
        };
}
$subs[3]->();

[download]

Question: what's the difference between $i and $j, don't they both have the same scope?

bw, bliako

In reply to Re: Strange behavior of iteration while creating Perl/Tk widgets dynamically by bliako
in thread Strange behavior of iteration while creating Perl/Tk widgets dynamically by Vasek

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