Store the output states (off/on as 0,1) in an array and convert to decimal when you make a change. Something like this perhaps

#!perl
use strict;

my @io = (1,0,0,0,0,0,0,0); # all off
switch(3,1); # left light on
switch(3,0); # left light off
switch(4,1); # left bell on
switch(4,0); # left bell off
switch(3,1); # left light on
switch(4,1); # left bell on
switch(3,0); # left light off
switch(4,0); # left bell off

sub switch {
  $io[$_[0]] = $_[1];
  my $num = oct('0b'.join '',@io); # bin to dec
  my $cmd = '<f 1108 '.$num.'>';
  print $cmd."\n";
  #$port->write($cmd);
  #$port->lookclear();
}
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