To keep things maintainable we split our program in modules, classes, functions… In perlsub from the execellent perl documentation you can lookup the syntax of how to use functions. Offcourse, you have to digg pretty deep to find out how you can pass a filehandle

# clientproc(*STDOUT);
# pass the socket

sub clientproc  
  $fh = shift;  
  print $fh 'hello world';