# Both have the following pragmas in place:
#!/usr/bin/perl -w
use strict;
use Carp;

#=================================================
#Version 1: no extra variable (slightly confusing)
#=================================================

   # Get the keys of @_
   foreach (keys %{ +{ @_ } }) {
      # Check to see if a key has a leading underscore
      ($self->{"_$_"} = ${ +{@_} }{$_}),next if (exists $self->{"_$_"});

      # Check to see if a key has no leading underscore
      (exists $self->{$_})          ?
       $self->{$_} = ${ +{@_} }{$_} :
      # Warn the user if the key isn't valid
       carp "The entry $_ is not a valid key.\n";
   }


#================================
# Version 2: a spare %tmp to help
#================================

   # Get the keys of @_
   my %tmp = ( @_ );
   foreach (keys %tmp) {
      # Check to see if a key has a leading underscore
      ($self->{"_$_"} = $tmp{$_}),next if exists $self->{"_$_"};

      # Check to see if a key has no leading underscore
      (exists $self->{$_})         ?
         $self->{$_} = $tmp{$_}    :
      # Warn the user if the key isn't valid
         carp "The entry $_ is not a valid key.\n";
   }