in reply to PDL's error or mine?

I can confirm the behaviour in PDL 2.081 (latest). The whole intersect is weird. 
1 and [1 1]: [1 1]
[1] and [1 1]: [1 1]
[1 1 1 1] and [1 1]: [1 1]
[0 1 2 3] and [1 1]: [1]

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map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

In Section Seekers of Perl Wisdom