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What I am trying to do is modify the regular expression of:
[0-9]{3}( |-|)[0-9]{2}( |-|)[0-9]{4}(?![0-9])
to ignore strings that start with HSF.

What I have tried:

The best I can come up with is:

( |-|^|[^HSF])[0-9]{3}( |-|)[0-9]{2}( |-|)[0-9]{4}(?![0-9])
here are the results:

123121234 <- works fine, and is found by the regex

lksjfd 123121234 lksjdf <- works fine, and is found by the regex

hello world123121234bleh bleh bleh <- This is what is causing me concern. The substring of d123 is getting caught up in the regex but I do not want it.

you are a ding dong. HSF123121234 <- This is a sample string that I do NOT want to get caught by the regex.
Updated 14-Dec-22 5:46am

Depending on the browsers you need to support, a negative lookbehind seems to work:
(?<!HSF)[0-9]{3}( |-|)[0-9]{2}( |-|)[0-9]{4}(?![0-9])
Assertions - JavaScript | MDN[^]
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To add to what Richard has said, if you are going to use Regular Expressions, then get a copy of Expresso[^] - it's free, and it examines and generates Regular expressions.
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