OK. While at this point, it will seem quite obvious. I'm going to list it, for completeness. As I would have thought it the first thing to show up. :)

Here cant i declare a variabe without using my keyword.

Error: Global symbol "$i" requires explicit package name at for.pl line 6.

Technically, you can

use strict;
use warnings;


my $number=8;
no strict; # could have also used "no strict vars"
$i=0;   #if i remove my keyword it gives error (not now)
for($i=0;$i<20;$i++)
use strict; # back to strict
{
        print "present value of the number is:";
        print $number++;
        print "\n";
}
[download]

OR, clobber them all up front:

use strict;
no strict vars;
use warnings;


$number=8; # look MA, no MY!
$i=0;   #if i remove my keyword it gives error -- not NOW!
for($i=0;$i<20;$i++) # here either
{
        print "present value of the number is:";
        print $number++;
        print "\n";
}
[download]

OK those were pretty much directly from the strictures documentation (which is why I felt they should have been included here). But why not illustrate another possibility -- global Variable Scoping in Perl: the basics?

#!/usr/bin/perl -w

our ( $number, $i );
use strict;

$number=8; # NOTE the absence of my
$i=0;   # AGAIN no my used here
for($i=0;$i<20;$i++) # OR here
{
        print "present value of the number is:";
        print $number++;
        print "\n";
}
[download]

Cool, huh? Well, not really. While the PHP language practically encourages global variables. In most cases, it should be avoided. If for no other reason; security reasons. Ovid has written a nice overview, that outlines global variables scoping, titled: 'our' is not 'my', that better describes this.

There. Now this feels complete :)

--Chris