For perl5.10

perl -Mre=debug -e "qr/a .{1,10} \ /x;qr/a .{1,10} [ ]/x;"

[download]

gives

Compiling REx "a .{1,10} \ "
Final program:
   1: EXACT <a> (3)
   3: CURLY {1,10} (6)
   5:   REG_ANY (0)
   6: EXACT < > (8)
   8: END (0)
anchored "a" at 0 floating " " at 2..11 (checking floating) minlen 3
Compiling REx "a .{1,10} [ ]"
Final program:
   1: EXACT <a> (3)
   3: CURLY {1,10} (6)
   5:   REG_ANY (0)
   6: EXACT < > (8)
   8: END (0)

[download]

So the two compile to the identical program under 5.10. And indeed, when I take out class_nodot, I get:

            Rate literal   class
literal 531978/s      --     -1%
class   539600/s      1%      --

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In reply to Re^3: The cost of unchecked best practices by Corion
in thread The cost of unchecked best practices by moritz

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