c@(Net URLPathEncoder traits) convert
[ | byte1 byte2 byte3 digit1 digit2|
  [c in isAtEnd] whileFalse:
    [byte1: c in next.
     byte1 caseOf: {
       $+ -> [c out nextPut: $\s].
       $% -> [byte2: c in next.
              byte3: c in next.
              digit1: (byte2 toDigit: 16).
              digit2: (byte3 toDigit: 16).
              digit1 isNil \/ [digit2 isNil] ifTrue: [error: 'Error reading hex sequence after %'].
              c out nextPut: (digit1 * 16 + digit2 as: c out elementType)].
     } otherwise: [c out nextPut: byte1].
     ].
].