~$ perl -E 'sub x { 3.14 }; use POSIX qw(setlocale LC_NUMERIC); say x; setlocale(LC_NUMERIC, ""); say x; setlocale(LC_NUMERIC, "C"); say x; setlocale(LC_NUMERIC, ""); say x; say x . ""; ' 
3.14
3,14
3.14
3,14
3,14