open IPFILE,'<',"/tmp/ipfile.txt";
my @ip_list = <IPFILE>;
close IPFILE;

foreach my $ip_in_list ( @ip_list ) {
   ...
  ($session, $error) = Net::SNMP->session( -hostname => $ip_in_list,
        ... => ...,
        .. all other options ...;
         );

$newval = $session->get_request(
                  [-callback        => sub {},]
                  [-delay           => $seconds,]
                  [-contextengineid => $engine_id,]
                  [-contextname     => $name,]
                  -varbindlist      => \@oids,
                              );

# now do something with the data found in $newval
# use -callback to point to a subroutine where you put further operations to be carried out on $newval

}