R: parallel foreach on list names does not work, but regular for loop runs successfully

Question

I'm trying to run PCA on two large datasets derived from the same parent dataset earlier in the script. I would like to perform the PCA in parallel on each of the objects, but for some reason I can't get it to work. The code block runs successfully and produces the expected output if run with a regular for loop, but each one takes about 1h to run, and I'd like to take advantage of the server's capacity, as I have to do this bot ~15 datasets.

---

This is my code:

selectObject <- function(object) {

                if(object == "scaled") {
                         scaling <<- "_scaleOnly"
                         pca.result <<- "pca.scaled"
                         object.path <<- path.scaled.object
                } 

                if(object == "scaled.regressed") {

                         scaling <<- "_scale_nUMIregress"
                         pca.result <<- "pca.scaled.regressed"
                         object.path <<- path.scaled.regressed.object

                 }
}

---

seurat.objects <- list(scaled=seurat.object.scale,
                  scaled.regressed=seurat.object.scale.regress
                  )


library(foreach)
library(doParallel)

cores <- detectCores()
cl <- makeCluster(2)
doParallel::registerDoParallel(cl)

foreach(object=names(seurat.objects)) %dopar% {

    print(object)

    selectObject(object)

    print(paste(object, pca.result, scaling, pca.path))


    assign(pca.result,
      doFastPCA(t(seurat.objects[[object]]@scale.data))
    )


    saveRDS(pca.result, 
            paste0("/path/to/pcaObject.", age, scaling, ".Rds")

    )

}

The above stalls forever without producing even the very first print() output, and when I cancel the process with ^C, I get the following error:

Error: "'...' used in an incorrect context"

But, if I replace the foreach line with:

for (object in names(seurat.objects)) {

[everything as above]

}

then it runs successfully, albeit sequentially.

What am I doing wrong?