Covering all code paths is not necessarily possible. The range of possible value may be environment dependent and too large to test in any reasonable amount of time. Consider the following:

sub makeUserSelectedObjectDance {
   # ENVIRONMENT DEPENDENT!!!
   # any class in @INC that has a dance method will be accepted
   my ($sClass) = @_;
   return if ! ($sClass->can('dance'));

   my $oDancer = $sClass->new();
   $oDancer->dance();
   return $oSomething;
}
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or consider this routine which allows any valid combination of class and method. This kind of thing isn't all that uncommon when coding event-driven frameworks:

sub applyUserSelectedActionToUserSelectedTarget {
   # ENVIRONMENT DEPENDENT!!! - relative to codebase size and contents
   # number of valid parings of class and method can be quite large
   # in a large codebase
   my ($sClass, $sMethod) = @_;
   my $crMethod = $sClass->can($sMethod);
   return if ! $crMethod;

   my $oSomething = $sClass->new();
   $oSomething->$crMethod();
   return $oSomething;
}
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Best, beth

Devel::NYTProf has worked wonders for me in similar situations - especially if you include the nytprofhtml program, which makes a browsable, annotated html document for all the code usage, including summary lists of all code called, how many times etc..., which will give you the dependancies you need.

Although as Joost says this obviously depends on the tests being up to scratch!