sub safe_isa {
    my($value, $class) = @_;
    eval { $value->can('isa') }
      ? $value->isa($class)
      : UNIVERSAL::isa($value, $class);
  }
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Note that calling $value->isa($class) directly blows up when $value is not an object, and a ref() check is insufficient to distinguish between blessed and unblessed references.

An alternative approach would use Scalar-List-Utils to replace the eval with: defined(Scalar::Util::blessed($value))

Hugo