For SLE 15 SP6 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:kanku:perl/SLE_15_SP6/devel:kanku:perl.repo
zypper refresh
zypper install perl-Filesys-Notify-Simple
For SLE 15 SP5 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:kanku:perl/SLE_15_SP5/devel:kanku:perl.repo
zypper refresh
zypper install perl-Filesys-Notify-Simple
For SLE 15 SP4 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/devel:kanku:perl/SLE_15_SP4/devel:kanku:perl.repo
zypper refresh
zypper install perl-Filesys-Notify-Simple