Select Code to Download

! /usr/bin/perl -w

...
__END__
produces:
undefined=2, defined=3

#! /usr/bin/perl -w

...
        grep => ' by_grep( \%h ) ',
    }
);

by_for:  undefined=2000300, defined=7999700
by_grep: undefined=2000300, defined=7999700
...
         Rate  for grep
for  163521/s   -- -27%
grep 224222/s  37%   --

cmpthese( -300, {
        byfor  => sub { by_for( \%h ) },
        bygrep => sub { by_grep( \%h ) },
    }
);

by_for:  undefined=2398233, defined=9601767
by_grep: undefined=2398233, defined=9601767
...
       s/iter bygrep  byfor
bygrep   24.1     --   -35%
byfor    15.6    55%     --

sub by_diff {
   my $h = shift;
...
       bydiff => sub { by_diff( \%h ) },
   }
);

by_for:  undefined=2398740, defined=9601260
by_grep: undefined=2398740, defined=9601260
...
bygrep   24.1     --   -35%   -51%
byfor    15.6    55%     --   -24%
bydiff   11.9   103%    31%     --