identifier can contain weird things

@ string ( @f0/0\:0 = "foo" )
@string { foo = "foo" # @f0/0\:0 }

@ preamble( 
        foo 
)
@preamble  { foo }

entry can be empty

@misc{}

key can be empty

@misc(,)

key can contain weird things

@misc( (}cr@zy{,)
@misc{ ()cr@zy{,}

Now testing entries with unknown type.

@cr@zy {key1,
    year = 2010,
    title = @f0/0\:0 # "jou{"}rn@l" # { {j}our"n@{l} } # @f0/0\:0,
    author = "Jœhn
    
    Nash",
}

@comment{ This is a comment

    The following line starts a new entry, even though few parsers will catch it
        @article{key2,
           year = "2010",
}

we are now outside of an entry again, balancedness does not matter
}
} @ comment

The next line defines an entry of type "comment<at>article"
@  commment@article {key3,}