Here is a simple Perl module file named Foo.pm:

package Foo;

use warnings;
use strict;

require Exporter;
our @ISA         = qw(Exporter);
our @EXPORT_OK   = qw(bar);

sub bar {
    my $x = shift;
    if ($x > 10) {
        return 'big';
    }
    else {
        print 'small';
    }
}

1;
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use warnings;
use strict;
use Foo qw(bar);
use Test::More tests => 2;

is(bar(77), 'big', 'check 77');
is(bar(22), 'big', 'check 22');
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Both of these files are in the same directory. Run the test with coverage as follows:

perl -MDevel::Cover test.pl
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I get this report as output:

It is a little verbose, but if you focus on the Foo.pm line, you'll see that only 50% of its branches were covered. This corresponds to the if branch inside the bar sub.

http://search.cpan.org/~pjcj/Devel-Cover-0.66/lib/Devel/Cover/Tutorial.pod

This tutorial should also be installed on your system.

Update: Nevermind... I see that this tutorial link was also in your PM node link, so you already know about that. In an attempt to make amends for this lame node, I have installed Devel::Cover and created a small test case to illustrate how to get it up and running quickly. See ... Re: Devel::Cover for Dummies (quick start)

how do I get started with it?

Well, that's pretty easy. Change to your module directory and run

cover -test
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Any code you run with -MDevel::Cover is automatically added to the coverage database. This means that sometimes you have to get creative to have Devel::Cover only record coverage for your code, instead of also recording coverage for prove, all of the Test:: modules you use, and so on.

If you use Module::Build, there's already a ./Build target that does the coverage for you. This is an example of a brand new module bootstrapped using Module::Starter's module-starter utility:

$ module-starter --module Foo --mb --author "some 1" --email 'some1@ex
+ample.com'
Created starter directories and files
$ cd Foo
$ perl Build.PL
Checking whether your kit is complete...
Looks good

Checking prerequisites...
Looks good

Creating new 'Build' script for 'Foo' version '0.01'
$ ./Build help |grep cover
  docs                           testcover   
  html                           testpodcoverage
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$ ./Build testcover
t/00-load.........ok 1/1# Testing Foo 0.01, Perl 5.010000, /usr/bin/pe
+rl     
t/00-load.........ok                                                  
+       
t/boilerplate.....ok                                                  
+       
t/pod-coverage....ok                                                  
+       
t/pod.............ok                                                  
+       
All tests successful.
Files=4, Tests=6,  8 wallclock secs ( 6.78 cusr +  0.45 csys =  7.23 C
+PU)
cover
Reading database from /home/hue/tmp/Foo/cover_db


---------------------------- ------ ------ ------ ------ ------ ------
+ ------
File                           stmt   bran   cond    sub    pod   time
+  total
---------------------------- ------ ------ ------ ------ ------ ------
+ ------
blib/lib/Foo.pm                75.0    n/a    n/a   50.0  100.0  100.0
+   71.4
Total                          75.0    n/a    n/a   50.0  100.0  100.0
+   71.4
---------------------------- ------ ------ ------ ------ ------ ------
+ ------


Writing HTML output to /home/hue/tmp/Foo/cover_db/coverage.html ...
done.
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$ ./Build testpodcoverage
1..1
ok 1 - Pod coverage on Foo
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