my @ranks[@array] = 5..10; is a syntax error.

c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"my @array = 0..5;
 my @ranks;
 @ranks[@array] = 5..10;
 dd \@ranks;
"
[5 .. 10]
[download]

Update: However, the following works for initializing a new lexical (reverse used just to add some variety):

c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"my @array = reverse 0 .. 5;
 my @ranks = (5 .. 10)[@array];
 dd \@ranks;
"
[10, 9, 8, 7, 6, 5]
[download]