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Regular Expression help (is a line end token being matched in the middle of a string?)

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Andrew
Andrew 2014-5-7
Hi all,
I've hit a lack of understanding on regular expressions and I'm hoping someone can help
If I start with a simple enough string:
str = 'Serial Number: NEO1B39100092'
I first check for the existence of my keyword:
keyword = '(\W|^)serial number:*(\W|$)+'
and then try to find its value with:
expr = ['(?<=', keyword, ')[^\s]+'] % N.B. using [^\s] as a template for '[^', delimiters ']'
for comparison, I'll use the keyword without the line end anchor
keyword2 = '(\W|^)serial number:*(\W)+'
expr2 = ['(?<=', keyword2, ')[^\s]+']
Now if I use regexpi to test the two expressions
value = regexpi(str, expr, 'match', 'once')
value2 = regexpi(str, expr2, 'match', 'once')
I see that
value = ':',
while
value2 = 'NEO1B39100092'
My take on this is that the line anchor '$' from the original keyword is being match with the letter r somehow. For it to return ' : ' the character before ' : ' must match (\W|$)+ , and it can't be the \W because expr2 gives the expected result.
Can anyone shed some light on this for me?
Thanks for any help, Andrew

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