Predeclaration and prototypes don't work for methods. See the Prototypes section of the perlsub manpage.

From perlsub:

Method calls are not influenced by prototypes either, because the function to be called is indeterminate at compile time, since the exact code called depends on inheritance.

In reply to Re: Can One Predeclare a Package's Methods? by converter
in thread Can One Predeclare a Package's Methods? by sierrathedog04

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