/\b/ is equivalent to /(?<=\w)(?!\w)|(?<!\w)(?=\w)/. Feel free to replace \w with a character class.

It would be tedious to have to write \\$keyword([^a-zA-Z]) and then have to substitute back $1 (because I do not want it eaten).

Don't eat it if you don't want add it back. Equivalent without eating: 

\\$keyword(?=[^a-zA-Z])

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But you surely meant 

\\$keyword(?![a-zA-Z])

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In general, it's easier to extract the keyword, then check if it's the one you want. 

\\([a-zA-Z]+)

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In reply to Re: Defining Characters in Word Boundary? by ikegami
in thread Defining Characters in Word Boundary? by iaw4

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