use strict;
use warnings;
use List::Util qw(reduce);

my @arr = qw(0 3 5 12 3 2 1);;
my $maxi = reduce { $arr[$a] > $arr[$b] ? $a : $b } (0..@arr-1);  
print "maximum i = $maxi  value=$arr[$maxi]\n";
# maximum i = 3  value=12