I often see functions that behave differently, depending on a certain parameter/fl

I often see functions that behave differently, depending on a certain parameter/flag being passed. In the LAPACK packages, this is done by passing a character to the function, say pass 'T' to operate on the transpose of the matrix etc. In another library, I saw that instead, they pass the symbol :T instead to do this. Is there a “Julia”-way to do this and what is the right syntax/advised way of passing flags to functions?

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