UiPath is built on .Net Engine and .NET regex engine does not support POSIX character classes. It only supports regular expression character classes. This is the reason you are not getting the output. You have [[:graph:]] which has to be replaced with \w or [A-Za-z]+
Often people gets confused with POSIX class and CHaracter class. [x-z0-9] is an example of a “character class” and [:digit:] is a POSIX character class, used inside a bracket expression like [x-z[:digit:]].
Try the below expression. This with provide values along with the field names.
Also use the OOTB UiPath activities IsMach and Marches instead of using a assign statement and writing custom VB code.