1)using input record separator as newline indicator is very interesting. Never seen it before but works well. Any reason? I am assuming it's just a style issue?

I guess it's more along "a \n is a \n is a \n" - $/ is a global, and that could be changed far away without you knowing it; so it's more safety than style.

2)Below code from tutorial does not work when I insert my next to variable.. can someone explain this?

You are allocating a lexical $x, not a package global (which would be either use vars '$x' or our $x), and local aliases only package globals. You can't (shouldn't) allocate globs and lexicals of the same name in the same scope:

our $x;
my $x; # gives a warning
[download]

our $x;
{
    my $x; # ok
}
[download]

3)can someone explain further on "lexical variables are declared at compile-time, not initialised? Is this because BEGIN runs during compile-time? I sneaked in a new my $foo = something inside of BEGIN block and execution of the code came out w/ foo is something during BEGIN phase

"lexical variables are declared at compile-time, not initialised" means "the container is created, but nothing is put into it". The initialization (= puting something into the bucket) happens at run time. BEGIN blocks are compiled and immediately run, that's why "code came out w/ foo is something during BEGIN phase".

See also my/local, space/time (was: Re: The difference between my and local).

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}