$ perl -MPOSIX=LC_NUMERIC,setlocale -E 'setlocale LC_NUMERIC,"de_DE"; printf "%.2f\n", 1'
1.00
$ perl -MPOSIX=LC_NUMERIC,setlocale -E 'setlocale LC_NUMERIC,"de"; printf "%.2f\n", 1'
1.00
$ perl -MPOSIX=LC_NUMERIC,setlocale -E 'setlocale LC_NUMERIC,""; printf "%.2f\n", 1'
1,00