The code below allows you to get the date at the start of the week given the ISO Week Number and optionally the year (defaulting to this year), and requires the DateTime module.

The first week of the year is defined by ISO as the one which contains the fourth day of January, which is why we get the fourth day of the year before working out which week we are interested in.

This subroutine will return the date at the start of the week, as a DateTime object. Feel free to take the code and use or modify it as you need.