It's seems weird to be advocating another non-Perl solution in so short a timespan, but this is something done obscenely easy with a shell script if your ping binary has appropriate permissions (they usually do)...

#!/bin/sh

PING='/bin/ping -c 5'   # FreeBSD/Linux
#PING='/usr/sbin/ping'  # Solaris

FETCHMAIL='/usr/local/bin/fetchmail -s -t 60'

$PING $hostname 1>/dev/null 2>&1 \
&& $FETCHMAIL
[download]

If you absolutely must write something in Perl, then I second blm's suggestion of Net::Ping::External (alt.).

    --k.