You never assigned to $_. The equivalent of 
sub scribble {
   while ( $a = shift ){
      $a; # has arg
   }
}

[download]
that assigns to $_ is 
sub scribble {
   while ( $_ = shift ){
      $_; # has arg
   }
}

[download]

In both cases, you are using global variables. $_ is particularly dangerous to clobber. Fix: 

sub scribble {
   local $_;
   while ( $_ = shift ){
      $_; # has arg
   }
}

[download]

In reply to Re: using shift and $_ in loop by ikegami
in thread using shift and $_ in loop by leocharre

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