regex - awk extract multiple groups from each line

How do I perform action on all matching groups when the pattern matches multiple times in a line?

To illustrate, I want to search for /Hello! (\d+)/ and use the numbers, for example, print them out or sum them, so for input

abcHello! 200 300 Hello! Hello! 400z3
ads

Hello! 0

If I decided to print them out, I'd expect the output of

200
400
0

Answer

This is a simple syntax, and every awk (nawk, mawk, gawk, etc) can use this.

{
    while (match($0, /Hello! [0-9]+/)) {
        pattern = substr($0, RSTART, RLENGTH);
        sub(/Hello! /, "", pattern);
        print pattern;
        $0 = substr($0, RSTART + RLENGTH);
    }
}