I think we would need to see your constructor and the way you build new objects to do a lot more debugging. In the absence of that information, here's where I'd focus my debugging: 
foreach my $day (@days) {
    my $day_data = $self->{cell_format}[$day];

    print STDERR "Changing hash $day_data for day $day!\n";

    @$day_data{keys %$format} = values %$format;
}

[download]
That way, you can compare the reference address for multiple accesses. (My bet is on something tricky in the constructor, though.)

In reply to Re: Strange method behavior by chromatic
in thread Strange method behavior by Trimbach

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