You can use eof to check for end of file. There is an example similar to what you want in the perldoc for eof. Something like:

# insert dashes just before last line of last file
while (<>) {
  # Do stuff with each line

  if (eof) {          # check for end of current file
    print "I am at the end of the file\n";
    close(ARGV);        # close or last; is needed if we
                        # are reading from the terminal
  }
}
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Update: Corrected eof() to eof