1 sub foo
2 {
4a    my $self = shift;
4b    my () = @_;
3 }

##</code><code>##

my $data_fh = IO::File->new($data_filename)
    || die "Cannot open '$data_filename' for reading: $!\n";

my $stuff = read_file_with_format($data_fh);

...

my $second_fh = IO::File->new($second_filename)
    || die "Cannot open '$second_filename' for reading: $!\n";

my $other_stuff = read_file_with_format($second_fh);

...

sub read_file_with_format
{
    my ($fh) = @_;

    ...
}