Multi-character field separators in sort

[Michael Muratet]

Greetings

I'm sure this question has come up, but I cannot find the answer in  
the archives. I have a make file generated by a third-party python  
script with the following line that I am trying to run in bash on  
CentOS 5.2:

set -o pipefail;  cat s_1_1_export.txt | \
        awk -F$'\t' '$13 != "" && $NF == "Y" {OFS="\t"; --NF; $13 =  
sprintf("%011d", $13+10000); print $0}' | \
        sort -T . --field-separator="      " --buffer-size=500M -k11,13 | \
        awk -F$'\t' '{OFS="\t"; $13 = $13-10000; print $0}'  >  
s_1_1_sorted.txt.tmp && mv s_1_1_sorted.txt.tmp s_1_1_sorted.txt

I am having two problems with the sort command. The first is that it  
reports sort: cannot create temporary file: ./sortdKFMLK: Permission  
denied. The directory permissions are wide open. I solved that by  
increasing the buffer to 1000M. The second problem persists. The 3- 
space field separator is generating an error, sort: multi-character  
tab '   ". I've found a lot of discussion about how various shells  
treat escaped characters, but I'm looking for a definitive statement  
that sort can handle separators with more than one character (or not).

I have v5.97 of the coreutils and b3.2.25(1) of bash.

Thanks

Mike