See perllol and perlreftut to begin.

A hash associates string keys with scalar values. So you can't embed a hash into another hash's value, directly. Instead, you embed a reference to a hash, since references are scalar.

A major help in learning the Perl data structures is Data::Dumper. Build a structure, dump it out to see how Perl understands it, in Perl syntax.

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[ e d @ h a l l e y . c c ]