Use the lvalue returned from the assignment, and test it for definedness: 
sub foo {
  defined(my $x = shift) or warn "No parameter given!"
  # ...
}

[download]
Of course, it still can't tell if the array was empty or if it shifted an undefined value off it.

In reply to Re: shift, undef and 'or die' by ariels
in thread shift, undef and 'or die' by agoth

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