For Each URL

The For Each URL action loops through the URLs contained in the found tag, optionally skipping duplicate URLs. The tags containing the URLs can be located at any depth inside the found tag. In each iteration, the appropriate tag is marked as a named tag.

Properties

The For Each URL action can be configured using the following properties:

URL Tags:
Specifies the HTML tags whose URLs to loop through.
First URL Number:
The number of the first URL to include in the loop. The number can be specified to count either forward from the first URL, or backward from the last URL.
Last URL Number:
The number of the last URL to include in the loop. The number can be specified to count either forward from the first URL, or backward from the last URL.
Loop Backwards:
Select that the loop should loop through the matching tags in reverse order. Please note that the loop will go through exactly the same tags as if it were looping forward just in reversed order. This means that the First Tag Number is referring to first tag in the selection of tags to loop over and not the first tag visited when looping (actually it will be the last).
URL Pattern:
A pattern to match against each URL. The Action property then determines whether the URL should be skipped or not. The pattern must match the entire URL. If no pattern is specified, no pattern matching is done.
Action:
If set to "Skip URLs that Match Pattern", all URLs that match the pattern will be skipped. If set to "Skip URLs that Do Not Match Pattern", all URLs that do not match the pattern will be skipped.
Skip Duplicate URLs:
Specifies whether duplicate URLs (i.e. multiple identical URLs) should be skipped and hence not be looped through. Check this property the same URL should not be looped through more than once. (This is usually the case.)
Tag Name:
Has two options, Auto or Named.
Auto gives the tag a name which is number. The first Auto-numbered tag will have number 1, the next number 2 etc. Note that the number may change if additional Auto-numbered tags are inserted before this step (on the same page).
Named gives the tag a fixed and explicitly stated name, which has several advantages:
Keep Existing Named Tags:
If this option is selected, existing named tags are kept along with the named tag marking the result of each iteration. If this option is not selected, existing named tags are removed, and each output state will only contain the named tag marking the result of the iteration.

Videos

Following is a video giving a basic introduction to looping.