Your best source for sample Perl code is probably the Code Wizard. It is especially applicable if you are writing a custom probe in Perl, which is probably not true in your case. But you can still see what libraries to use and such.
Invoking a callback from Perl should look something like this:
my $pds_out = pdsCreate();
pdsPut_PCH($pds_out, 'name', 'cdm' );
pdsPut_PCH($pds_out, 'section', '/setup' );
pdsPut_PCH($pds_out, 'key', 'loglevel');
pdsPut_PCH($pds_out, 'value', '5' );
my($rc, $pds_in) = nimNamedRequest($robot_addr, 'probe_config_set', $pds_out, 10);
if ( $rc ) {
print "ERROR updating config: ", nimError2Txt($rc), "\n";
} else {
print "Config updated\n";
}