Fellow boriz
Thank you very much for your suggestion, but I'm not sure if

perl -MData::Dumper -e "print Dumper @{$_[3]}{'a','b','c','d'}, $_[3];
+ "
$VAR1 = undef;
$VAR2 = undef;
$VAR3 = undef;
$VAR4 = undef;
$VAR1 = undef;
$VAR2 = undef;
$VAR3 = undef;
$VAR4 = undef;
$VAR1 = undef;
$VAR2 = undef;
$VAR3 = undef;
$VAR4 = undef;
$VAR5 = '1';
[download]

perl -MData::Dumper -e 'print Dumper @$data{"a","b","c"}, $data'
$VAR1 = undef;
$VAR2 = undef;
$VAR3 = undef;
$VAR4 = {
          'c' => undef,
          'a' => undef,
          'b' => undef
        };
[download]

Your $data and @_ are empty here, so this won't work the same because of autovivication. The number of $VAR variables is different, because you have a .. d in the first and a .. c in the second expample.

All of this should work if you actually fill $data and $_[3] with a hash reference that uses those keys.

"What should it profit a man, if he should win a flame war, yet lose his cool?"

Autovivification shouldn't fill in the data structure as I access it? So both the accesses should produce the same data structures (that's autovivification work, I guess), and Data::Dumper should produce the same result in both cases.

BTW, here is the result, again:

perl -MData::Dumper
$data = { a=>'b', c=>'d', e=>'h', i=>'j' };
$_[3] = { a=>'b', c=>'d', e=>'h', i=>'j' };
print Dumper @$data{'a','c','e'};
print "\n";
print Dumper @{$_[3]}{'a','c','e'};
print "\n";
[download]

and the result was:

$VAR1 = 'b';
$VAR2 = 'd';
$VAR3 = 'h';

$VAR1 = 'b';
$VAR2 = 'd';
$VAR3 = 'h';
[download]

exactly as expected. I'm confused. What's the problem with auto-vivification? Its supposed to fill in the "gore details", it isn't?

Thank you for your time and patience!

-- monsieur_champs

My perl works this way, Im sure there is another mistake.

#!/usr/bin/perl

use Data::Dumper;

%xx = ( a => 1, b => 2 );

sub inputBox{
    @{$_[3]}{'a','b','c','d'};
}
sub inputBox2{
  my $data = $_[3];
    @$data{'a','b','c','d'};
}
print Dumper (inputBox( 1,2,3,\%xx));
print Dumper (inputBox2( 1,2,3,\%xx));
[download]

Boris