I'm in the process of learning Perl (5.8) in my spare time and as a mental (and spiritual) excercise I am attempting to design a regular expression that will enable me to convert raw "METAR" weather reports into something that is more human readable.

I know how to do the legwork to make this possible... but I have a question about efficiency.

I'm breaking this task down into sections. For each section I am using "named capture" to cache each important value to a variable. This works nicely. But due to the (very) complex nature of the METAR standard, I am forced to use many levels of nested grouping.

So my question is, can I speed up the following...

m/((xxxxxxxx)(yyyyyyyy)(zzzzzzzz))/

...by using "non-capturing parentheses" for the groups below the outer nesting level?...

m/((?:xxxxxxxx)(?:yyyyyyyy)(?:zzzzzzzz))/

I've reduced my problem down to basic principles as best I can. As I understand it, the outer parentheses will still capture everything inside.

So, is that second regex pattern more efficient than the first?

I would benchmark this myself normally, but I'm only about 20% of the way through designing the entire regex for METAR codes and I don't want to go too far down "the wrong path" if you see what I mean.

Advice gratefully received.

Wossy. :)
ps. METAR codes specification: (http://www.ofcm.gov/fmh-1/fmh1.htm see chapter 12 if you're interested, although the entire document is very interesting in itself).

In reply to Speeding up a large regex match pattern by wossname

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