use strict;
use warnings;
my %hash=("one" =>1, "two"=>,2);
my %hash_tr_fr=(one=>"une","two"=>"deux");
for my $eng (keys %hash){
   $hash{$hash_tr_fr{$eng}}=$hash{$eng};
   delete $hash{$eng};
}
use Data::Dumper;
print Dumper(\%hash);