From type/Int

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multi sub    unival(Int:D  --> Numeric)
multi method unival(Int:D: --> Numeric)

Returns the number represented by the Unicode codepoint with the given integer number, or NaN if it does not represent a number.

say ord("¾").unival;    # OUTPUT: «0.75␤» 
say 190.unival;         # OUTPUT: «0.75␤» 
say unival(65);         # OUTPUT: «NaN␤»

From type/Str

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multi method unival(Str:D: --> Numeric)

Returns the numeric value that the first codepoint in the invocant represents, or NaN if it's not numeric.

say '4'.unival;     # OUTPUT: «4␤» 
say '¾'.unival;     # OUTPUT: «0.75␤» 
say 'a'.unival;     # OUTPUT: «NaN␤»