Convert Arcminute / Second to decimal (irregular format)

I'm dealing with some irregular and poorly thought through data with GPS coordinates and I need to make them more useable and pipeable.

I've been basing my work on the angle2dec function that I found on here:

angle2dec <- function(angle) {
  angle <- as.character(angle)
  x <- do.call(rbind, strsplit(angle, split=' '))

  #decimal points where they should and should not be here
  #causes my issue as i can't use a consistent string split
  #character.  splitting the first 3 '.' occurrences might work

  x <- apply(x, 1L, function(y) {
    y <- as.numeric(y)
    y[1] + y[2]/60 + y[3]/3600
  })
  return(x)
}

However my data is not nicely formatted. A coordinate looks like this:

'53.17.35.852'

The ang2dec function works for coordinates that follow this format:

ang2dec('53 17 35.852') = 53.29329

(This is the correct result)

Clearly the problem is the poor choice of formatting of the coordinate. Can anyone suggest a way that I can convert the first format of coordinate into the second or propose changes to the ang2dec function that would include the functionality that I am looking for?