for my $i ( 0 .. $#$proj ) {
   my $time = $dbh->selectall_arrayref($stmt, {Slice => {}}, $project_id);

   my @users;  # Create a new array every pass through the loop.
   
   for my $j ( 0 .. $#$time ) {
      push @users, $time->[$j];
   }

   $proj->[$i]{'users'} = \@users;
}

##</code><code>##

for my $i ( 0 .. $#$proj ) {
   my $time = $dbh->selectall_arrayref($stmt, {Slice => {}}, $project_id);
   $proj->[$i]{'users'} = $time;
}