Better is 
eval { local $SIG{__DIE__}; $ref->isa('Some::Package'); }

[download]
You might trigger a die handler, which could be bad. For example, one of Test::More's dependencies has one. See eval-blocks and Test::Builder for more on the topic.
My criteria for good software:
  1. Does it work?
  2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

In reply to Re^2: How to tell if a variable is blessed ? by dragonchild
in thread How to tell if a variable is blessed ? by jeanluca

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