Most people seem more or less happy with the ActiveState binary distributions for win32. Cygwin is another, and it has the advantage of a C compiler, a unix-alike shell, and make. Learning to use cygwin is a significant commitment.

Most scripts written for 5.6 work fine in 5.8. If you used nothing marked 'deprecated', the worst you will see is warning of newly deprecated misfeatures. The perldelta docs will tell you what has changed.