C:\test>perl -le"printf qq[%010u\n], $_ for 1 .. 1e6" >1e6x10.txt

C:\test>dir 1e6x10.txt
17/05/2012  18:13        12,000,000 1e6x10.txt

C:\test>perl -MDevel::Size=total_size -e"@a=<>; print total_size \@a" 1e6x10.txt
72000176