Off topic: Perhaps single char positive character classes should be optimized to be equivalent to a literal character? Perhaps something can be done about single char negative character classes too.

Update: Corion sent me a message saying he thought this was already done in 5.10, so I put it to the test. Indeed, it is.

Test code used: (Same as OP accept avoided extra sub calls) 

#!/usr/bin/perl

use strict;
use warnings;

use Benchmark qw( cmpthese );

our $line = ('a' x 500) . ' ' . ('a' x 20);

sub code { "use strict; use warnings; $_[0]; 1;" }

cmpthese -2, {
    literal     => code(' our $line =~ / a .{1,10}     \   /x;   '),
    class       => code(' our $line =~ / a .{1,10}     [ ] /x;   '),
    class_nodot => code(' our $line =~ / a [^\n]{1,10} [ ] /smx; '),
};

[download]
>c:\progs\perl588\bin\perl 674979.pl
                Rate class_nodot       class     literal
class_nodot   2206/s          --        -44%       -100%
class         3908/s         77%          --       -100%
literal     805341/s      36409%      20507%          --

>c:\progs\perl5100\bin\perl 674979.pl
                Rate class_nodot     literal       class
class_nodot 618394/s          --        -12%        -13%
literal     704734/s         14%          --         -1%
class       708360/s         15%          1%          --

[download]

In reply to Re: The cost of unchecked best practices by ikegami
in thread The cost of unchecked best practices by moritz

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