There is, in fact, a grep function.

See:

• perldoc perlfunc
• perldoc -f grep
• perldoc -f map

Incidentally, since lists usually contain references to the things that they “contain,” I often design filtering-routines so that they scan through the input list, selecting what they want to keep and pushing those onto an output list, which is then returned.   Since we’re only moving references around, we aren’t burning up memory.   And, the process is non-destructive:   at the end of the day, we have the output list but the input list hasn’t actually been touched.   We can now, if we choose, discard the one and keep the other, or we can keep both.