C:\>chcp
Active code page: 437

C:\>perl -MScalar::Util=looks_like_number -wE "use utf8; say looks_like_number('ç')? 'yes' : 'no'"
no

C:\>bash
$ perl -MScalar::Util=looks_like_number -wE 'use utf8; say looks_like_number("ç") ? "yes" : "no"'
Malformed UTF-8 character (1 byte, need 3, after start byte 0xe7) at -e line 1.
no
$ exit

C:\>