s/^/604375146618424928110766602983870727725667231901941561316236180836680951044276307718174243403123136593503653142226854524673706961790023941104078370652478992085606212570656397248761889074006370471472192093985361783660394122980219875666980838272377998885153153538207781991786760045215487480163574218/
/249$/{s//750/;y/0123456789/9876543210/;}
/999/s/./9/g
Note that non-ascii characters in the above source code will be escaped (such as \x9f).