When installing application, there are addon available but are there easy ways to find out what are they like (Libsvg-perl in the application "Inkscape") Thanks!
The package name, which can be found between the brackets, will tell you more about the add-on. Search for this package name in the Software Center. Below the package details are a list of add-ons. The one you mention (Libsvg-perl) is visible in the screenshot below:
For any add-ons you want info on, just re-do your search for that package name.