in reply to Re: How do I match a expression start with $a and not contain $b after $a
in thread How do I match a expression start with $a and not contain $b after $a

At the risk of death, you need a /s modifier if you want the intermediate junk to be able to include returns.

Also you should be using \Q and \E escapes. 

/\Q$a\E(?!.*\Q$b\E)/s

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(The mistake of using $a and $b for normal use was the fault of the questioner, and not you.)
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