textproc/p5-Unicode-CaseFold 1.01nb9 NetBSD

What is Case-Folding?

In non-Unicode contexts, a common idiom to compare two strings case-insensitively is lc($this) eq lc($that). Before comparing two strings we normalize them to an all-lowercase version. "Hello", "HELLO", and "HeLlO" all have the same lowercase form ("hello"), so it doesn't matter which one we start with; they are all equal to one another after lc.

In Unicode, things aren't so simple. A Unicode character might have mappings for uppercase, lowercase, and titlecase, and the lowercase mapping of the uppercase mapping of a given character might not be the character that you started with! For example lc(uc("\N{LATIN SMALL LETTER SHARP S")) is "ss", not the eszett we started off with! Case-folding is a part of the Unicode standard that allows any two strings that differ from one another only by case to map to the same "case-folded" form, even when those strings include characters with complex case-mappings.