Ahh, not a horrible idea for simple patterns. I would need to add a ^ at the beginning and maintain a $ at the end of the RE. For a simple enough pattern I could even generate the partial REs programatically. Alas, it would be tougher to deal with quantifiers, capturing groups, etc, and, alas, I am quite the fan of quantifiers.

(It took me a while to recognize what you were suggesting. I didn't notice the ".=" in $tre .= shift @tre.)