One useful way to think of a module is as a collection of related subroutines. They should be designed to be easy to use by any programmer without regards to the internals. Now think about a script which looks like this:

#!/usr/bin/perl

use warnings;
use strict;

my @files = find_files(shift);
foreach my $file (@files) {
    eval { process_file($file) };
    die "Could not process $file: $@" if $@;
}

sub find_files {
    ....
}

sub process_file {
    ....
}
[download]

With that, you have reused whatever code you have in &process_file. That's good. But what if another program needs the same functionality?

package My::FileProcessor;

use strict;
use warnings;

use base 'Exporter';
our @EXPORT_OK = qw(find_files process_file);


sub find_files {
    ....
}

sub process_file {
    ....
}

1;
[download]

And your original code becomes this:

#!/usr/bin/perl

use warnings;
use strict;

use My::FileProcessor qw(find_files process_file);

my @files = find_files(shift);
foreach my $file (@files) {
    eval { process_file($file) };
    die "Could not process $file: $@" if $@;
}
[download]

That code is now shorter, but more importantly, other programs can more easily share the functionality provided by My::FileProcessor.

Does that help?

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