Re^3: A plague on all your features

I don't know why the hints are undef for c, but I can confirm it's accurate.

$ diff -u \
   <( perl -MO=Concise,b b.pl 2>&1 ) \
   <( perl -MO=Concise,c b.pl 2>&1 )
--- /dev/fd/63  2023-03-06 20:59:39.932888013 -0400
+++ /dev/fd/62  2023-03-06 20:59:39.932888013 -0400
@@ -1,8 +1,8 @@
 b.pl syntax OK
-main::b:
+main::c:
 5  <1> leavesub[1 ref] K/REFC,1 ->(end)
 -     <@> lineseq KP ->5
-1        <;> nextstate(main 1252 b.pl:15) v:%,*,&,x*,x&,x$,fea=15 ->2
+1        <;> nextstate(main 1257 b.pl:16) v:*,&,x*,x&,x$,fea=1 ->2
 4        <1> entersub KS ->5
 -           <1> ex-list K ->4
 2              <0> pushmark s ->3
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Note the different value of the hints (fea= for "feature") for the two lines.

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Re^4: A plague on all your features by ikegami (Patriarch) on Mar 07, 2023 at 01:04 UTC
Actually, the whole `v:` thing is the hints, not just the `fea=` portion. And we see another difference: The `%`. Not sure what it means, but it relates to `%^H`. Presumably the presence of `%^H`. Again, present for `b` but not `c`.	[reply] [d/l] [select]
Re^5: A plague on all your features by ikegami (Patriarch) on Mar 07, 2023 at 01:17 UTC
`b` has a `%^H` and `c` doesn't. The extra time spent is clearly spent accessing (copying?) this hash. Why doesn't `c` have a `%^H`? Some hints are found in `$^H` and some are in `%^H`. I think what's happening is that `use 5.010;` avoids creating `%^H` just to set flags that are on by default (such as `indirect`). `use feature ":5:10";`, on the other hand, clearly does create this hash. There's a problem with this answer. `say` and a couple other flags which aren't set by default appear to be in `%^H`. Maybe they are found in both `$^H` and `%^H`?	[reply] [d/l] [select]