my @filters = ( \&eliminate_ws, \&do_something, \&do_something_else, \&etc );
# ...
while (<$myfile>)
{
  FILTERS: for my $filter (@filters)
  {
    # keep filtering until a filter says to stop.
    last FILTERS unless $filter->()
  }
}

sub eliminate_ws { s/\s*$// } # always returns true.
# as opposed to:
# sub eliminate_ws { s/\s+$//; 1 } # always returns true, even if s "failed"

##</code><code>##

$ perl -e 'printf "%e\n",((1/334000)-(1/1211000))'
2.168248e-06