marto@Shemp:~$ perl -MJSON::PP -e 'print $JSON::PP::VERSION'
2.97001marto@Shemp:~$ 
marto@Shemp:~$ PERL_JSON_BACKEND=JSON::PP perl -MData::Dump=dump -MJSON -E 'my $json = JSON->new;@foo=$json->incr_parse(q!{"check_result!); $bar=$json->incr_parse(q!" : "ok"}!); dump $bar'
{ check_result => "ok" }

... after a cpanm JSON::PP

marto@Shemp:~$ perl -MJSON::PP -e 'print $JSON::PP::VERSION'
4.00
marto@ShempPERL_JSON_BACKEND=JSON::PP perl -MData::Dump=dump -MJSON -E 'my $json = JSON->new;@foo=$json->incr_parse(q!{"check_result!); $bar=$json->incr_parse(q!" : "ok"}!); dump $bar'
{ check_result => "ok" }
marto@Shemp:~$ perl -v

This is perl 5, version 26, subversion 1 (v5.26.1) built for i686-linux-gnu-thread-multi-64int