With the default collations in MySQL (e.g. utf8_general_ci), strings will be matched case-insensitively:

WHERE col IN ('IT', 'Ruby') will match “it” and “ruby”.

For case-sensitive matches, each string must be preceded by the keyword BINARY:

WHERE col IN (BINARY 'IT', BINARY 'Ruby')

Caveat: I would guess that BINARY affects the matching of strings with combining characters (same character, different byte representation).