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I'm the wrong person to ask, but I would assume so, as they (substr refs) have steadily been corrected and improved over the last few versions.
They have been available since before my time (5.6.1), but through a bug in the implementation, there was originally only 1 lvalue ref available at a time for each given string in te program. This was fixed in 5.8.5.
The most useful use of them is processing fixed length record files where you allocate the input buffer and create an array of lvalue refs to the fields. You can now read or sysread subsequent records directly into the buffer overlaying the previous record, and the fields array now refers to the fields of the new record.
It saves re-divvying the buffer over and over for each record, which can save a good deal of memory (re)allocation when processing large files. Add a few seeks and you have an efficient and fairly cache freindly way of doing in-place editing on huge, fixed record length files.
Not they're much in vogue these days, but they do have their uses :). I played with manipulating huge tiff images like this one (Warning!!! 11,477 x 7,965 x 24 image 204MB) directly on disk.
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?
"Science is about questioning the status quo. Questioning authority".
The "good enough" maybe good enough for the now, and perfection maybe unobtainable, but that should not preclude us from striving for perfection, when time, circumstance or desire allow.