From type/Allomorph

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method tc(Allomorph:D:)

Calls Str.tc on the invocant's Str value.

From type/Cool

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sub tc(Str(Cool))
method tc()

Coerces the invocant (or in sub form, its argument) to Str, and returns it with the first letter case-folded to title case (or where not available, upper case).

say "abC".tc;       # OUTPUT: «AbC␤»

From type/Str

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multi sub    tc(Str:D  --> Str:D)
multi method tc(Str:D: --> Str:D)

Does a Unicode "titlecase" operation, that is changes the first character in the string to title case, or to upper case if the character has no title case mapping