Right now, in Perl, CPU cycles almost always do not matter.

In 1973, oil prices jumped from ~$3/barrel to $12/barrel. The worlds economy went into a downward spiral that would lasted ~7 years. Inflation was rampant throughout the world. Unemployment went through the roof in most Western Economies. Food prices rose at unprecedented rates.

In 1980, oil prices jumped from $15/barrel to $40/barrel. The world's economies went into downward sprials.

But still the world car industry, especially in the US, kept churning out 5 litre "shopping cars" return ~10 mpg. Imagine the savings in raw oil stocks if the lessons had been heeded and no new cars were produced from 1974 onwards, that used say, < 40mpg? How many billions of barrels of oil would that have saved?

Today, oil prices have recently peaked at $115/barrel. The price of rice, wheat and other basic foodstuffs has tripled in some places. Bread, milk, rice and all the foodstuffs produced from them, including meat, are rising weekly--some daily. The worlds banks are suffering meltdown due to bad deptsdebts. Inflation is threatening. Unemployment rising.

Some figures put the energy used by commercial computer and related equipment as 13% of the total energy consumption world wide. Wasted cycles == wasted energy. Both in the direct energy usage, and the indirect cost of dealing with the heat generated. Throwing hardware at performance problems without considering the possibility of optimisations (either better algorithms or better code), is exactly the same as building low-efficiency gas-guzzling car engines because they are, in the short term, "cheaper" to produce.

The lessons of history are free to learn for those that will.