For standard run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:cganapathi:branches:openSUSE:Leap:15.6/standard/home:cganapathi:branches:openSUSE:Leap:15.6.repo
zypper refresh
zypper install perl-Algorithm-Diff
For pool-leap-15.6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/home:cganapathi:branches:openSUSE:Leap:15.6/pool-leap-15.6/home:cganapathi:branches:openSUSE:Leap:15.6.repo
zypper refresh
zypper install perl-Algorithm-Diff