From perldoc Net::Ping

If the "icmp" protocol is specified, the ping() method sends
an icmp echo message to the remote host, which is what the
UNIX ping program does.  If the echoed message is received
from the remote host and the echoed information is correct,
the remote host is considered reachable.  Specifying the
"icmp" protocol requires that the program be run as root or
that the program be setuid to root.