You access complex structures with %flag_assignments as the root. Perl will helpfully bring intermediate elements into life automatically ("autovivify") if they don't exist.

In the following code, if $flag_assignments{$temp_key} does not exist, it will get autovivified due to its use a few lines later:

    ...
    if (defined $flag_assignments{$temp_key}) {
        print "KEY [$key] TK [$temp_key] TS [$temp_semester] FAS [$fla
+g_assignments{$temp_key}{starrez}] FAA [$flag_assignments{$temp_key}{
+abbreviation}]\n";
    }
    # Here it is possible that $flag_assignments{$temp_key} does not e
+xist
    
    
    # ONLY ONE FLAGE PER CATEGORY, AND GREEKS LIVING ON CAMPUS WILL AL
+SO GET NR ACCESS TO THE HOUSE OF THE FRAT/SORORITY

    if ($starrez{$key}{"dorm"} ne "None") {
        # Here, autovivification of a value for $flag_assignments{$tem
+p_key} happens
        # because it's part of $flag_assignments{$temp_key}{$temp_seme
+ster}
        if ($flag_assignments{$temp_key}{$temp_semester} ne "") {
...

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One approach to prevent autovivification is to use exists checks before accessing a complex data structure. Another could be to use Data::Diver. To prevent accidential autovivification, see autovivification.

In reply to Re: Not meaning to add values to a hash ("autovivification") by Corion
in thread Not meaning to add values to a hash by stu96art

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