The pack object is useful for combining int, float, and/or symbol messages into a single space-separated list. Messages that come in each inlet of pack are stored until a message comes in the left inlet, triggering output of the entire list.
Int, float, and list are all (normally hidden) message selectors that are assumed whenever Max encounters a message that consists of (respectively) a single int, a single float, or a multi-item message that starts with a number. Similarly, typing a single int, a single float, or any multi-item list that starts with a number directly into an object box assumes an object of type int (or i), float (or f), or list (or pack).
This example demonstrates how to separate items in a formatted message.
The regexp object makes a list that expresses rules for text matching and substitution, using a format that is valid in many computer languages. For example, if you have a list of integers that you want to list with no spaces in between, you can use the substitution string %0 to replace the match with an empty string.
If you have two lists that you want to combine, you can do so using zl object with an argument lace. However, it will only output a list that is twice as long as the shorter of the two lists. Hence, it's best if the two lists are the same length.