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my @kansas = qw( corn wheat hay cattle );
my @oklahoma = qw( wheat dairy cattle );
...
  my %hash = map{ $_=>1} @{$_[1]}; 
  return grep { !defined $hash{$_} }  @{$_[0]};
}

Benchmark: timing 100000 iterations of diff1, diff2...
     diff1:  2 wallclock secs ( 1.74 usr +  0.01 sys =  1.75 CPU)
     diff2:  3 wallclock secs ( 2.22 usr +  0.01 sys =  2.23 CPU)