Another idea is to have some other code generate the unreadable code. I've seen systems that generate accessor functions, in particular. Might as well generate the fastest code.

I would certainly go this way. The Makefile for the package can certainly include a small script that would turn sub setx { my ($self, $value) = @_; $self->{_x}=$value; } into sub setx { $_[0]->{_x} = $_[1] }

This is actually what I do for XML::Twig: the code I maintain is in Twig.pm.slow, and the Makefile.PL includes the following line:

Note the use of \$(PERL) which finds the proper perl even if the command is /usr/local/bin/weird-perl Makefile.PL instead of the perl that's in the path.

speedup does things like:

$SET_FIELD="first_child|next_sibling|pcdata|cdata|ent|data|target|comm
+ent|flushed";
s{(\$[a-z_]+(?:\[\d\])?)             # $1: the object
   ->set_($SET_FIELD)                # $2: the field to set
   \(([^)]*)\)}                      # $3: the value (must not include
+ ())
 {$1\->\{$2\}= $3}gx;
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This replaces proper accessors by direct access to the hash.