There's another problem with if () elsif () elsif () ... else chains that bears mentioning.

It's an artifact of the way Perl source code is compiled down into the form used by the bytecode interpreter running underneath. The problem is that if any expression in any of the elsif conditions throws a warning (for instance, performing a comparison with a variable set to undef will emit an "Uninitialized variable" warning), then perl will report that the problem occurred on the line containing the if, not the actual line in question.

This is, as you can imagine, a royal pain when debugging if you're not aware of the quirk. In fact it causes a steady trickle of bug reports to be filed. The perl5-porters are currently evaluating how much extra memory it would take to save the additional line number information (that is currently being discarded) into the resulting bytecode in order to report the correct line number. So it may be fixed one day, but until then, dispatch tables are a good way of avoiding this gotcha.

• another intruder with the mooring in the heart of the Perl

In reply to Re^2: Hash option/menu loop weird or useful? by grinder
in thread Hash option/menu loop wierd or usefull? by mulander

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