In terms of performance, and maintenance, with a variable set of $type's mapping to a variable set of subroutines that need to be invoked, I would combine and enhance two of your approaches to be:

my %dispatch_table = (
    'apple'      => [\&a, ...],
    'orange'     => [\&o, ...],
    ...
);
while (defined($object = read one)) {
    $_->($object) for @{$dispatch_table{$type}};
}

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This approach avoids using a large amount of memory up front to read all objects in to memory, and dispatches using a hash lookup, which will ensure that dispatching is far more linear in terms of number of possible $type values, than would be possible with a string of if, elsif, elsif, ... would be.

Another small trick that I employ above, is to use the suffix modifier form of the for() loop. Although in theory, for(){statement;} should be as fast as statement for();, it is not. The second does not use a block, and avoids some of the block overhead by using simpler op codes underneath.

In reply to Re: performance - loops, sub refs, symbol tables, and if/elses by MarkM
in thread performance - loops, sub refs, symbol tables, and if/elses by jaa

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