Re^4: Best practice for reading delimited file

prematch is just a wordier name for $`

$PREMATCH is the same as $` but it's not the same as ${^PREMATCH}:

* $PREMATCH
* $`

The string preceding whatever was matched by the last
successful pattern match, not counting any matches hidden
within a BLOCK or eval enclosed by the current BLOCK.

The use of this variable anywhere in a program imposes a
considerable performance penalty on all regular expression
matches. To avoid this penalty, you can extract the same
substring by using @-. Starting with Perl v5.10.0, you can
use the /p match flag and the ${^PREMATCH} variable to do
the same thing for particular match operations.
[download]

Source: perlvar.

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Re^5: Best practice for reading delimited file by SuicideJunkie (Vicar) on Oct 16, 2013 at 18:11 UTC
Ah, nifty! Since Perl v5.10.0, you can use the /p match operator flag and the ${^PREMATCH} , ${^MATCH} , and ${^POSTMATCH} variables instead so you only suffer the performance penalties. Is that sentence missing a "once" at the end perhaps?	[reply]
Re^6: Best practice for reading delimited file by Jenda (Abbot) on Oct 17, 2013 at 11:17 UTC
I think it's missing "for this regexp, not for all regexps anywhere in your script+modules". Jenda Enoch was right! Enjoy the last years of Rome.	[reply]
Re^6: Best practice for reading delimited file by Kenosis (Priest) on Oct 16, 2013 at 19:06 UTC
That certainly is a curiously obscure assertion, given the performance statements a bit later in the documentation. I think you're correct that something is missing here, but I'm not sure it's "once at the end".	[reply]
Re^7: Best practice for reading delimited file by SuicideJunkie (Vicar) on Oct 16, 2013 at 21:18 UTC
Its just that that's the first thing you see when doing a search-find for the name. It makes it sound like you get all the performance penalties associated with $`. If it has all the same penalties as before then its clearly bad to use, so further details don't really matter. ;)	[reply] [d/l]