$ perl -e '
    my @hashes;
    my @days = ([1,2,3], [], [], [4,5,6]);
    for (0 .. $#days) {
        my %x = (day => 1+$_);
        @x{qw{bal pay tot}}
            = @{$days[$_]} ? @{$days[$_]} : ("-") x 3;
        push @hashes, \%x;
    }
    use Data::Dump;
    dd \@hashes;
'
[
  { bal => 1, day => 1, pay => 2, tot => 3 },
  { bal => "-", day => 2, pay => "-", tot => "-" },
  { bal => "-", day => 3, pay => "-", tot => "-" },
  { bal => 4, day => 4, pay => 5, tot => 6 },
]