Maybe you're thinking of multi-level structures.

Here is an example for the OPer to play with to gain definition concerning the existence of the truth of all this:

>perl -wMstrict -le
"my %hash = qw(a 1 b 2);
 print 'true 1st level' if $hash{c};
 print exists $hash{c} ? '' : 'NOT ', 'exists 1 c';
 print 'true 2nd level' if $hash{c}{d};
 print exists $hash{c}    ? '' : 'NOT ', 'exists 2 c';
 print exists $hash{c}{d} ? '' : 'NOT ', 'exists 2 d';
"
NOT exists 1 c
exists 2 c
NOT exists 2 d
[download]

And substitute something like
    ... if $hash{c} == 42;
for
    print 'true 1st level' if $hash{c};
to see the effects of an actual comparison versus a simple truth test.