Well you asked for the "why" not for the "how" ... :)

I took a look into the Panther book and experimented with Devel::Peek and the implementation of aliases seems simpler than a magic data structure of type alias.

Arrays (AVs) are composed from C-structures with pointers to C-structure(s) realizing scalars (SVs).

So $_[0]=666 updates the underlying scalar ( what I called "assigning" ) while @_=(666) creates the pointer to a new scalar ( "setting" ).

In the following dump the scalar value for $x is held within SV = IV(0x88f2498) at 0x88f249c

The array's first slot will point to that same structure before and after updating with $_[0]=666 (#markers added)

<Reveal this spoiler or all spoilers in this node or all in this thread>

But creating new entries with @_=(666) will replace the pointer in this AV-slot to a new SV.

<Reveal this spoiler>

I hope the "how" is clearer now! :)

Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)

PS: Je suis Charlie!

In reply to Re^4: Accessing Arguments inside Subroutines via @_ by LanX
in thread Accessing Arguments inside Subroutines via @_ by citi2015

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