From the Mail::Internet manual page:

METHODS
       body ( [ BODY ] )
           Returns the body of the message. This is a reference
           to an array.  Each entry in the array represents a
           single line in the message.
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So you will have to derefence the body first, like this:

@content = @{$message -> body};
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It would have been much more convenient if the body method was context aware, and returned a list in list context. But c'est la vie. You could ask the author of the package to add this feature.

Abigail