As moritz already pointed out, this just relies on the way that the incrementer works on characters. Your code can be reduced a little further by using the preincrementor within the map, although it won't solve the problem with 'z' becoming 'aa'. But tighter still would be to just use a for:

#!/usr/bin/perl
use 5.12.0;
my @rot = qw(a v c g h t);
$_++ for @rot;
say @rot;
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- Miller