What's the difference between grep and map in Perl?

Question

In Perl both grep and map take an expression and a list, and evaluate the expression for each element of the list.

What is the difference b

Answer 1

I find that it's helpful to think think about grep() and map() in their most general form:

grep {BLOCK} LIST   
map  {BLOCK} LIST

grep() is a filter: it returns the subset of items from LIST for which BLOCK returns true.

map() is a mapping function: send a value from LIST into BLOCK, and BLOCK returns a list of 0 or more values; the combined set of all of those calls to BLOCK will be the ultimate list returned by map().