Thanks BrowserUK, I thought I was going crazy. I wonder if the extra factor might be the tabs themselves, as I can still get an out-of-memory error by replacing the join with manual tabs:

use strict;

my %hash1;
my %hash2;
my %hash3;

my @data = (0 .. 5000);

for (my $i = 0; $i < scalar(@data); $i++ ) {
        for (my $j = $i; $j < scalar(@data); $j++) {
                $hash1{ $data[$i] }{ $data[$j] } = 0;
                $hash2{ $data[$i] }{ $data[$j] } = 0;
                $hash3{ $data[$i] }{ $data[$j] } = 0;
                }
        }

print "Finished building hashes\n";

while ( my( $key1, $val1 ) = each %hash1 ) {
    while ( my( $key2, $val2 ) = each %$val1 ) {
        die 'Autovivify' unless exists $hash1{ $key1 }
                            and exists $hash1{ $key1 }{ $key2 };
        print "$key1\t$key2\t$hash1{ $key1 }{ $key2 }\t$hash2{ $key1 }
+{ $key2 }\t$hash3{ $key1 }{ $key2 }\n";
    }
}

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In reply to Re^2: Memory Error Printing Multiple Hashes Simultaneously by bernanke01
in thread Memory Error Printing Multiple Hashes Simultaneously by bernanke01

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