what do u mean by current block?

A block is a set of statements that are contained between a pair of braces. Blocks can be associated with subroutines, loops, conditionals and a number of other Perl constructs. There is also an implicit block around all of the code in a file.

our (like my) is lexically scoped, this means that its effects are only felt until the end of the innermost enclosing block.

I understand "my" is used for local variable.
so is "our" a global variable??

Pretty much. It exposes package variables within a given block. The differences between package and lexical variables and the subtle differences between my, local and our can get a little complex. I recommend you read the section on "Scoped Variable Declarations" that starts on p130 of the 3rd edition of the Camel.

--
<http://www.dave.org.uk>

"The first rule of Perl club is you don't talk about Perl club."