C:\test>wc -l 986831-01.dat
    268 986831-01.dat

C:\test>perl -nle" rand() < 0.1 and print" 986831-01.dat | wc -l
     33

C:\test>perl -nle" rand() < 0.1 and print" 986831-01.dat | wc -l
     26

C:\test>perl -nle" rand() < 0.1 and print" 986831-01.dat | wc -l
     32

C:\test>perl -nle" rand() < 0.1 and print" 986831-01.dat | wc -l
     24