It’s easy to define pyrrhic. Firstly, you should define the main foot, and then you will find where this foot “breaks” in some way. When you see 2 unstressed syllables standing together and if they do not fit the main foot, be sure that this is a pyrrhic.
To a green thought in a green shade.
The Garden by Andrew Marvell
My way is to begin with the beginning.
Don Juan by Lord Byron