In Str§

See primary documentation in context for routine parse-base

multi        parse-base(Str:D $num, Int:D $radix --> Numeric)
multi method parse-base(Str:D $num: Int:D $radix --> Numeric)

Performs the reverse of base by converting a string with a base-$radix number to its Numeric equivalent. Will fail if radix is not in range 2..36 or if the string being parsed contains characters that are not valid for the specified base.

1337.base(32).parse-base(32).say; # OUTPUT: «1337␤»
'Raku'.parse-base(36).say;        # OUTPUT: «1273422␤»
'FF.DD'.parse-base(16).say;       # OUTPUT: «255.863281␤»

See also: syntax for number literals