I don't understand your description of your requirement, but most likely you don't want to use a for loop but instead a while loop:

my $i = 0;
my $limit = 100,
while( $i <= $limit ) {
    $i++;

    if( $v and $i == $limit ) {
        $limit = 200;
    };
};
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Using a "magic" value like that sounds like a nasty hack to avoid an extra variable. Show us the context where the 2 * $i hack is important and we'll show you a cleaner way to achieve the goal.

As others have mentioned Perl offers a much cleaner for loop over a list: for my $index (0 .. 100) which makes the loop constraints clearer and less error prone. Adding a flag variable such as $hadEvent means the loop variable is just a loop variable and the intent of the "magic" is obvious, in fact not even magic any more.

Are you sure about the value of $v? Have you printed it out and examined it?

I can't see the point in incrementing a counter variable after the end of the loop, but a more natural way to write your loop in Perl would be:

my $i = 0;
for ( 1 .. 100 ) {
    $i++;
    # statements

    $i = 200 if $i == 100 and defined $v;
}
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Hope this helps!

Thanks for your replies folks. In the above code, once $i is incremented to 101, it won't hit the condition

 

if $i == 100 and defined $v;
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I wanted to execute the statements after the above pasted code, once $i becomes 101 to 200

$ perl -e 'my $v = 1;
> for ($i = 0; $i <=100; $i++) {
>     $i = 2* $i if defined $v and $i == 100;
> }
> print $i;'
201
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Having said that, you probably don't really want to use a C-style for loop for that, but rather a while loop.

First it is very odd for the "for loop" variable, in this case, $i to have scope outside of the for loop. Normally these things are coded as:  for (my $i=0; $i <=100; $i++){} #after the "for loop", $i has no scope.

But as another point, in Perl, C Style "for loops" themselves are rare. Usually better coded as for my $i (0..100){}. These C style for loops are very error prone critters, due to the "off by one" errors that can happen.

In this case, there is of course no need to check for $i==100 within the loop. That only happens on the last loop iteration. So this is the same thing:

my $i;
for ($i = 0; $i <=100; $i++)
{
    statements ...    
}
$i = 200 if defined ($v); #same thing as your code
                          #$i is 101 here, but it was
                          #100 on last loop iteration
                          #test can be moved outside of the loop
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