Comparing: 

( list ) x!! cond
( grep cond, list )
cond ? ( list ) : ()

[download]

I think I'd rather "reuse" the well-known grep for this case than adopt the more cryptic idiom you've invented. For your example case, I much prefer something that uses: 

join '/', grep defined $_, ...

[download]

Rather than repeating most of the terms twice (and repeating x!! and defined).

- tye        

In reply to Re: Secret Perl Operators: the boolean list squash operator, x!! (grep) by tye
in thread Secret Perl Operators: the boolean list squash operator, x!! by Aristotle

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