in reply to repeat data at one line and grep as pre-set format
I think you want to split each pair of data points out to a line on its own instead of having multiple datapoints on one line.
cat yourfile.txt | perl -ple 's/(\S+\s+\S+)\s+/$1\n/g'
should do this for you as long as you have even numbers of datapoints on each line
echo "00000001 99888 00000011 99889 00000002 99890 00000003 998
| perl -ple 's/(\S+\s+\S+)\s+/$1\n/g'
Pereant, qui ante nos nostra dixerunt!