my ($i) = map { $_->[0] } sort { $b->[1] <=> $a->[1] } map { [ $_ , $arr[$_] ] } 0..$#arr-1;

I don't understand the  0..$#arr-1 expression in the quoted statement. Did you mean  0..$#arr or  0..@arr-1 instead?

c:\@Work\Perl\monks>perl -wMstrict -le
"my @arr = (1,2,3,5,10,3,4,300,1,2,-2);
 my ($i) = map { $_->[0] } sort { $b->[1] <=> $a->[1] } map { [ $_ , $
+arr[$_] ] } 0..$#arr-1;
 print qq{i of largest == $i (\@arr[$i] == $arr[$i])};
"
i of largest == 7 (@arr[7] == 300)

c:\@Work\Perl\monks>perl -wMstrict -le
"my @arr = (1,2,3,5,10,3,4,300,1,2,-2, 999);
 my ($i) = map { $_->[0] } sort { $b->[1] <=> $a->[1] } map { [ $_ , $
+arr[$_] ] } 0..$#arr-1;
 print qq{i of largest == $i (\@arr[$i] == $arr[$i])};
"
i of largest == 7 (@arr[7] == 300)
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