Esteemed monks,

After playing with JSON::RPC::Client and obtaining the error "value is type str, expected real" (not sure if the error comes from client validation or from the server but that doesn't matter) I investigated and found that Data::Dumper was turning my floating point parameters into strings. I tried changing a couple of configuration variables listed in the module's documentation and was surprised to find that Useperl solves the problem:

use warnings;
use strict;
use Data::Dumper;
use JSON;

my $json = JSON->new;
for my $up (0, 1) {
    print "useperl: $up\n"; $Data::Dumper::Useperl = $up;
    my $data = { foo => 'bar', qux => 0.42 };

    printf "before: '%s'\n", $json->encode ($data);
    Dumper $data;
    #Data::Dumper->Dump ([$data], ['data']);
    printf "after:  '%s'\n", $json->encode ($data);
}
__END__
useperl: 0
before: '{"qux":0.42,"foo":"bar"}'
after:  '{"qux":"0.42","foo":"bar"}'
useperl: 1
before: '{"qux":0.42,"foo":"bar"}'
after:  '{"qux":0.42,"foo":"bar"}'
[download]

Both Dumper and Data::Dumper->Dump show this effect. When working with integers, we get more consistent results:

use JSON;
my $json = JSON->new;
for my $up (0, 1) {
    print "useperl: $up\n"; $Data::Dumper::Useperl = $up;
    my $data = { foo => 'bar', qux => 42 };

    printf "before: '%s'\n", $json->encode ($data);
    Dumper $data;
    #Data::Dumper->Dump ([$data], ['data']);
    printf "after:  '%s'\n", $json->encode ($data);
}
__END__
useperl: 0
before: '{"qux":42,"foo":"bar"}'
after:  '{"qux":42,"foo":"bar"}'
useperl: 1
before: '{"qux":42,"foo":"bar"}'
after:  '{"qux":42,"foo":"bar"}'
[download]

Is this difference in behaviour to be expected?