sub mass_init (\%\@$);

my @init_to_toto = qw{ a b c f t u };

my %hash = ( y => 'pre', z => 'pre', );
mass_init(%hash, @init_to_toto,      'toto');
mass_init(%hash, @{[ qw(b g k p) ]}, 'TITI');

use Data::Dumper;
print Dumper \%hash;

sub mass_init (\%\@$) {
  my ($hashref, $arrayref, $string) = @_;
  # $hashref->{$_} = $string for @$arrayref;
  @{ %$hashref }{ @$arrayref } = ($string) x @$arrayref;
  }

##</code><code>##

$VAR1 = {
          'a' => 'toto',
          'y' => 'pre',
          'p' => 'TITI',
          'c' => 'toto',
          'u' => 'toto',
          'k' => 'TITI',
          'g' => 'TITI',
          'b' => 'TITI',
          'z' => 'pre',
          'f' => 'toto',
          't' => 'toto'
        };