It's undef because the hash reference is a value returned from an SQL query. If no rows are selected (for instance), then it's possible for the 'id' value to be undef. And when I perform some math operation (as noted by Marshall below), the warning is triggered. I could wrap the math operation code around a conditional to suppress the warning:

if ($some_href->{id}) {
    if ($some_href->{id} > 0) {
        do_something();
    }
}

[download]
But I'm not sure if that's better than using ||=.

In reply to Re^4: What is the difference between |= and ||=? by Anonymous Monk
in thread What is the difference between |= and ||=? by Anonymous Monk

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