My usual rule for recursion is to check if we are done first, then recurse.

For this problem, it avoids "Use of uninitialized value in print..." which isn't checked for :)

#!/usr/bin/perl

# http://perlmonks.org/?node_id=1203005

use strict;
use warnings;

inter([1],[1,2],[1,2,3],[1,2,3,4,5]);

sub inter { @_ && inter( grep { @$_ && print shift @$_ } @_ ) }
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