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Postings from June 2013
On Sat, Jun 22, 2013 at 07:07:53AM -0700, Wallace Reis wrote:
> The performance penalty introduced by English.pm for regular
> expressions was fixed in 5.18, so update docs about it (without
> needing to use "-no_match_vars" special flag) and pointing
> to English.pm docs where necessary.
Actually that's not strictly true.
The full fix for $`,$&,$' performance issues involves the new COW
mechanism, which was disabled by default in 5.18 (and enabled by default
in 5.19.1).
5.18.0 has a partial fix, where it records the presence of the three vars
separately.
So in 5.18.0, this is fast:
perl5180o -e'$&; $a="a"x1_000_000; 1 while $a =~ /a/g;'
this is extremely slow:
perl5180o -e'$`; $a="a"x1_000_000; 1 while $a =~ /a/g;'
On 5.19.1, they're both fast.
Even if had been fixed in 5.18.0, I think that the text in perlvars
warning that in older versions the puncuation vars are slow, should be
kept.
--
"There's something wrong with our bloody ships today, Chatfield."
-- Admiral Beatty at the Battle of Jutland, 31st May 1916.
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