Hi xerophyte,

I hope this is not homework. Some suggestions that I could quickly come up with are:

• Use "use strict;" and "use warnings;" in the code (atleast during development).
• Minor nitpick: Use a better named variable than "$errorstate". Using "$errorstate = 1" to indicate that valid sshport was input is confusing. I would have used a name like "$isvalidport", etc.
• Instead of reading in the port value from <STDIN>, pass it as a cmdline argument.
• Port numbers are limited to 65535 max. So, a value larger than that should be treated as invalid data.
• Instead of using s/.../.../ to modify $_, why not print the new line "Port $sshport" to SSHD_CONFIG_NEW directly? I feel the substition operation is not required. The current print statement can be moved inside an else block.
• Please close the opened file handles before calling rename(...)
• You should check the return status of the rename(...) command.

Regards,
Mahesh