So, you basically want to allow a @ as long as it's not preceeded by whitespace? \b will not do that -- that just forces a word character to be present.

Suggestion (untried): 

text: /[^@\n]*(?:\S@[^@\n]*)*/

[download]
That still allows text like: 
foo bar@

[download]
I cannot deduce whether you want to allow that or not.

It's not the most efficient regex, as it typically will backtrack one character on each (valid) @ character encountered. But since Parse::RecDescent is a massive backtracking engine written in Perl, this is likely to be acceptable.

In reply to Re: Parse::RecDescent: problem with grammar and error reporting by JavaFan
in thread Parse::RecDescent: problem with grammar and error reporting by kikuchiyo

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