'our' and 'my' are two very different beasts. You can not substitute 'our' with 'my' or vice versa, take this as an example:

use strict;
{
   our $y;
   $y = 17;
   print "Inner: $y\n";
}

our $y;
print "Outer: $y\n";
[download]

That will print:
Inner: 17
Outer: 17
Now, if you substituted our with my (s/our/my/g) then it would print:
Inner: 17
Outer:
...and it would complain about use of uninitialized variable :-)

Autark.