The perl guide document "perlpacktut" contain the following command statements, which look like assignments.

    $UTF8{Euro} = pack( 'U', 0x20AC );
    # Equivalent to: $UTF8{Euro} = "\x{20ac}";

    $Unicode{Euro} = unpack( 'U', $UTF8{Euro} );
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The tokens `$UTF8{Euro}` and `$Unicode{Euro}` seem to be treated as variables. However, the typical perl variables I am familiar with are of the form $v or ${v} but not $v{u}. In fact, the following code ends up with an error.

    #!/usr/bin/perl

    my $v{u} = "hello";
    print($v{u}, "\n");
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syntax error at ./test.pl line 3, near "$v{u"

What are `$UTF8{Euro}` and `$Unicode{Euro}`? Which perl guide document explain this kind of token?

Thank you in advance.