Anomalous Difference in Output between HTML Files Created by 'cover'

[Jim Keenan]

I have just noticed an anomalous difference in output between two of the 
files created by the Devel::Cover 'cover' utility when run against a 
popular Perl module -- and I am wondering whether this difference should 
be considered a feature or a bug.

The module in question is Text::Template, which I am studying as part of 
Perl Seminar NY's contribution to the Phalanx project.  Start with a 
copy of Text-Template-1.44 (the latest on CPAN) and examine the code. 
In 'lib/Text/Template.pm', consider these two lines:

  128    $self->_acquire_data unless $self->{DATA_ACQUIRED};
  450        if (! defined $val) {
Proceed in the normal manner:
  perl Makefile.PL
  make
  cover -delete
  HARNESS_PERL_SWITCHES=-MDevel::Cover make test
  cover
... 'cover' creates a number of HTML files, including these two:
  ./Text-Template-1.44/cover_db/blib-lib-Text-Template-pm.html
  ./Text-Template-1.44/cover_db/blib-lib-Text-Template-pm--branch.html
'blib-lib-Text-Template-pm.html' displays lines 128 and 450 exactly as 
they appear in the module itself. 
'blib-lib-Text-Template-pm--branch.html', however, displays the relevant 
branch part of these lines of code as follows:

  128  unless $$self{'DATA_ACQUIRED'}
  450  if (not defined $val) { }
'$self->{DATA_ACQUIRED}' is changed to '$$self{'DATA_ACQUIRED'}' and '! 
defined $val' is changed to 'not defined $val'.  (I could site other 
examples as well, but these suffice to illustrate the point.)

Now, I grant that these are merely displays, not live code. 
Nonetheless, since the purpose of these HTML files is to guide a 
programmer to lines of code whose test coverage needs improvement, I am 
puzzled as to why the output in these two files differs.

Jim Keenan