CPU's may still be getting marginally faster; but typical data files are increasing in size at a much faster rate.

My personal take is that seldom used and one-off requested features should not impact the performance unless those features are being used!

This is easily accomplished by having the minimal/most-used functionality -- the fast(est) version of a primary function or method -- as the default; and then have the added-functionality version override that if and when it is required.

Eg.

sub function_fast { ... }
sub function_full {
   ...
   function_fast( ... ); ## If possible, else copy-paste common code d
+espite the DRY principle...
   ...
}
sub function;

sub function_init {
    my %args = @_;

    validate_args( \%args );

    if( added_functionality_required ) {
        *function = \&function_fast;
    }
    else {
        *function = \*function_full;
    }
}
[download]

Poor example code, but hopefully explains my drift.