"Do you really expect someone to play guessing games with the output of a command list? Do you expect poor ammalu89 to go away and read the documentation for everyone on the list before piecing together your so called strategy? Seems like you have no interest in either helping the user, backing up your claim that FTP can do this reliably or proving your assertion that comparing the number of bytes is a logical way of comparing files.
True. This sort of thing is not for the uninitiated. Users of Perl shouldn't be bothered to be required to read the perltoot, or perlootut before making inquiries. Which also speaks to your second assertion (just above). The (sub) commands modtime, and size; while not perfect, will give one at least a sense, as to whether the remote file is different (has changed, been modified) since their last inquiry. It's not perfect, but it's also not as bad as you seem to assert.
And my "correction" does indicate that FTP is not just for "downloading files", as you initially claimed in your first reply to the OP.
¡λɐp ʇɑəɹ⅁ ɐ əʌɐɥ puɐ ʻꜱdləɥ ꜱᴉɥʇ ədoH