I am not sure how you did you get the output "{ "cat" : "text – abcd" }". Just now I tried with binmode but I've got the same error again(see below).

text ΤΗτ abcd

Would you please try this code and confirm again please. 
use strict;
use warnings;
use utf8;
use JSON;
my $data = "text – abcd";
binmode STDOUT, ":utf8";
print "$data";

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please remember the char mentioned in the statement ("text – abcd")is not a regular dash.

In reply to Re^2: malformed UTF-8 character in JSON string in perl by Yllar
in thread malformed UTF-8 character in JSON string in perl by Yllar

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