I spent several hours chasing down a simple bug in my Parse::RecDescent (P::RD) grammar. It turned out that in one of my subrules, I wrote:
equals:        '>=' | '<=' | '=' | '>' | '>'

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Note the duplication of the '>' symbol. This works fine in Perl (`perl -e 'print 0 || "hi" || "hi"'`), but apparently P::RD didn't really like it. Finally, jcwren showed me my stupid error. I changed the second '>' to '<' and everything magically worked.

But it left me wondering why this would cause the rule not to work correctly. After all, it works in Perl.

Is there anyone familiar with the inner workings of Parse::RecDescent who would care to shine a light on this seemingly mysterious behavior?


I realize that P::RD is only supposed to work on correct grammar, and this certainly wasn't correct (technically). But this should at least be considered a GOTCHA in the docs, and if possible, should be the target of some error-checking code in the next release.

Thanks!

Quinn Slack
perl -e 's ssfhjok qupyrqs&&tr sfjkohpyuqrspitnrapj"hs&&eval&&s&&&'

In reply to Parse::RecDescent gotcha? - duplicates in ORs by qslack

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