In this post it's said that precompiling your regular expressions will improve script performance. The author proves it by performance test. However, as far as I understand, the post is talking about the cases when you use your regular expressions repeatedly. What if there are lots of regular expressions in the script, but each is used only once? Will there be a performance benefit in precompiling regex which is used only once throughout the script?
If it's only used once - then just use regexp literal.
Your point is valid - it only makes sense when you use the same regular expression a lot.