Capturing Data In Large Text File Between A Pattern

What do you want to do with the captured text?  Best to supply a sample file for input (doesn't have to be real, just representative of what to expect), and then a file (or other description) of what the output should be given the input file.

How many instances of the pattern will there be in the file?  Always two?  Or more?

One file could have as many as 300 INS instances. I need to capture all the lines after the initial INS up to the next. I have attached a small sample to explain my issue.
sample.txt

Use the regex object from the .Net framework with this pattern:

$re = [regex]'(?:^|\n)(INS(?:.|\n)+?)(?=\nINS)'

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You can use the object's matchall method to do the parsing you desire.  Then iterate the resulting groups/captures.

I'm still not getting what you want to do with the captured text?  In what form should it be passed down the pipeline?
The way I'm reading it, given your sample input file the output would just be the entire file.  Reading your description another way I would just exclude lines that have "INS".  Sorry, it's just not clear to me.

I need to break the entire file up into blocks of data with the "INS" as the delimiter. Not separate files, just one large file but with a start (INS) and finish (capturing all lines up to the next INS) for the accounts in the text file.

INS (start of first account)
second
third
fourth
fifth
INS (start of the next account)

There could be five lines or 20 lines, it all depends on the data that has changed for the users demographic information.

Exactly works as it needs.

Love this place, constantly learning and constantly impressed with the depth of knowledge here.  Thanks again!

OK, great!  Glad it's working for you.