Thank you everybody for your answers. Ended up with following:

sub format_output {
     my $var1 = shift;
     my $var2 = shift;
     my @array = @_;
     my $tmp = 0;
     for ($tmp = 0 ; $tmp <= $#array ; $tmp++) {
          do_good_stuff_to_array_elements;
     }
}

my @array = ();
# $scalar carries the binary data
@array = split('', $scalar);
&format_output(":", 0, @array[8 .. 13]);
[download]

Thanks again, Ronald Vazquez