Fellow monks, I seek enlightenment on how to generate a hash of hashes with constant keys. I have a list of countries in an array like so: @countries = (Algeria, Argentina...) which will form the keys of the inner hashes, and a file containing data in the following format: 
Q4_2001: 741 1203 3406 1861 1242 1911 601 etc 
Q3_2001: 773 1255 3552 1941 1296 1993 627 etc
Q2_2001: 805 1307 3698 2021 1350 2075 653 etc

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I would like to build this into a hash of hashes thus: 
%HoH = (
        Q4_2001 => {
                Algeria      => 741,
                Argentina    => 1203, etc
        },
        Q3_2001     => {
                Algeria      => 773,
                Argentina    => 1255, etc
        },
 );

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However, I am fairly new to Perl, and my attempts to write a sub to generate this HoH have not met with success, even after much perusal of perldsc, perllol, etc. Here's what I have so far: 
sub build_HoH {
    while (<DATA>) {
    next unless s/^(.*?):\s*//;
    my $period = $1;
    my @data = split;
    foreach my $country(@countries) { 
        $HoH{$period}{$country} = $data;
    }
}

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I would be grateful for any brotherly advice as to where I am going wrong. Humble thanks in advance.

In reply to building a hash of hashes with constant keys by mooseboy

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