The Harvest Broker requires some additional installation so that the WWW interface to the Broker will function correctly.
You'll need to edit $HARVEST_HOME/cgi-bin/HarvestGather.cgi. There are two variables that you may need to change, HARVEST_HOME and GZIP_PATH (the directory in which the GNU gzip program lives):
HARVEST_HOME=/usr/local/harvest
GZIP_PATH=/usr/local/bin
You may need to edit $HARVEST_HOME/cgi-bin/BrokerQuery.pl.cgi, to change the HARVEST_HOME variable near the top of that file. And if your Perl binary is not /usr/local/bin/perl then you'll need to change the first line of BrokerQuery.pl.cgi as appropriate.