bit shift operation on the status variable for IPC::Run

Question

I recently came across the following code for one of the perl module

  my @cat = qw( cat );
  use IPC::Run qw( run timeout );

   eval { run \@cmd, '<', "in.txt", \&out, \&err or die "cat: $?" };
  #here why status variable is being done Binary Shift Right
  my $status = $? >> 8;

I am unable to make why binary shift has been made.

Answer 1

I am unable to make why binary shift has been made.

Because you don't get the information you want if you don't.

$? contains three pieces of information:

• What signal killed the process ($? & 0x7F)
• Was a core dump produced (($? >> 7) & 1)
• Was error code was passed to exit ($? > 8)

Answer 2

It's to allow for 'nesting' of return codes.

So you can tell the difference between cat generating an error code, and run generating an error code (or whatever perl call you're making).