rexify for module installation doesn't work

(debian 9.5 / perl 5.24 / rex 1.6.0)
Running the command rexify --use="Rex::Ext::Backup" would result in:

malformed JSON string, neither tag, array, object, number, string or atom, at character offset 0 (before "(end of string)") at /usr/local/bin/rexify line 384.

Online I just found this workaround (manually copying the repo): https://groups.google.com/forum/#!topic/rex-users/794tvV45OxY

I did a little bit of poking in the rexify script, but (with my low level perl knowledge) didn't succeed. I don't see anything wrong with the JSON at http://modules.rexify.org/api/1.6/get/dep/Rex::Ext::Backup

#~line 368
  print "Getting dependencies for $name...\n";             
                                                           
 my $myOrigServerString= sprintf ($DEPEND_SERVER,$name); 
 #my $myServerString= to_json($myOrigServerString);      
 my $myServerString= $myOrigServerString;                
 print $myServerString ."\n";                              
 #my $myServerString= encode_json($$myLegacyServerString); 
                                                           
my $myJson = get( $myServerString);                        
print $myJson ."\n";                                       
=pod                                                       
my @testJson;                                              
$testJson[0] = qq\{"ok":"0"}\;                             
my $myRevJson = \@testJson;                                
use HTML::Entities;                                        
  my $deps = decode_entities( $myRevJson );                
=cut                                                       
my $deps = decode_json( $myJson );                         

Start by running rexify --use="Rex::Ext::Backup" with the reported Perl and Rex versions, then inspect the dependency-fetching code in rexify around line 384. Compare the response from the Rex module API endpoint with the JSON passed to the decoder; done means the command retrieves the dependency and completes installation without the malformed JSON error.