my $file = '/usr/dict/words';

#selecting a random line from a file
my $line = do {
  open FH, "<$file" or die "Could not open $file: $!";

  #Go to a random spot in the file
  seek FH, rand((-s FH) + 1), 0;
  
  #This forces us to the next line, because
  #we might be positioned in the middle of
  #a line in FH.
  <FH>;

  #If the next call to <FH> is about to
  #return a part of the last line in the
  #file, then wrap around to the beginning
  #of the file. We ONLY want complete lines.
  seek(FH, 0, 0) if eof;

  #Return the next available, complete, line
  <FH>;
};