Perl is great at manipulating strings, naturally. 
This string is 49 characters long.

Perl is great at manipulating strings, naturally. 
Perl begins at character 0 

Perl is great at manipulating strings, naturally. 
great begins at character 8 

Perl is great at manipulating strings, naturally. 
xxx begins at character -1 

Perl is great at manipulating strings, naturally. 
The first ing begins at character 26 
The last ing begins at character 33 

Perl is great at manipulating strings, naturally. 
The index of the first at is 11 and the final index is 40
After 11 characters, the index of the next at is 14 
After 40 characters, the index of the previous at is 24 

Perl is great at manipulating strings, naturally. 
Grabbed Pattern: is great starts at 5 and goes 8 chars 

Substituting is totally awesome staring at 5 and going 8 chars 
Perl is totally awesome at manipulating strings, naturally.