Oh wise monks, I am embarrassed, but my problem is this: 
use constant EX_TEMPLATE => 'II';
my $length = 8;
my %ValArrayByID = ();
# ... open file handle $fh, etc...
my $packed_data;
while (read($fh, $packed_data, $length)) {
my ($ID, $Val) = unpack EX_TEMPLATE, $packed_data;
not defined $ValArrayByID{$ID}
    and $ValArrayByID{$ID} = [];
push @{$ValArrayByID{$ID}}, $Val;
}
# ... close file and use my newly minted hash

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Above is my example code. The code reads in pairs of unsigned integers from a file and builds a hash of arrays. The file on disk is about 100 meg, and I think reading in 8 bytes at a time is killing the IO. How can I make this speedy?

In reply to Unpacking small chucks of data quickly by Anonymous Monk

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