But you can do 
sub iseq {
  (!defined $_[0] || $_[0].9) eq (!defined $_[1] || $_[1].9);
}

[download]
Update - shorter: 
  1 == keys %{{map {(!defined()||$_.9)=>1} @_}};

[download]
Caution: Contents may have been coded under pressure.

In reply to Re^2: undef-safe equality (shorter) by Roy Johnson
in thread undef-safe equality by hubb0r

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