Redundant regex ([0-9]{2} | [0-9] {2, 4})?

Popcorn Dave has asked for the wisdom of the Perl Monks concerning the following question:

Fellow monks,

I was surfing around Yahoo Answers the other day and a person was asking for an explanation of what the following regex did:

s/^\[[0-9]{2}-[0-9]-{2}-([0-9]{2} | [0-9] {2, 4})\]\s+//;
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Of course I pointed him towards YAPE::Regex and presented him with the explanation output, but what struck me as odd was the

([0-9]{2} | [0-9] {2, 4})
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Unless I'm mistaken, you're matching 2 numbers or between 2 and 4 numbers. Why would use the | there? If you're matching between 2 and 4 numbers you're matching 2 already aren't you? Am I just missing something here?

To disagree, one doesn't have to be disagreeable - Barry Goldwater

Comment on Redundant regex ([0-9]{2} \| [0-9] {2, 4})? Select or Download Code

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Re: Redundant regex ([0-9]{2} \| [0-9] {2, 4})? by ikegami (Patriarch) on Feb 26, 2009 at 22:42 UTC
No, `/[0-9]{2} /` does not match a subset of what `/ [0-9] {2, 4}/` matches. `/[0-9]{2} /` only matches `"99\x{20}"`, where `9` can by any digit 0-9 `/ [0-9] {2, 4}/` only matches `"\x{20}9\x{20}{2,\x{20}4}"`, where `9` can by any digit 0-9 Update: Fixed copy and paste bug in in second item.	[reply] [d/l] [select]
Re^2: Redundant regex ([0-9]{2} \| [0-9] {2, 4})? by Popcorn Dave (Abbot) on Feb 27, 2009 at 00:34 UTC
Holy crap, I need glasses! I completely missed the space in there and didn't realize it until I increased the font size. That makes perfect sense now. Duh. To disagree, one doesn't have to be disagreeable - Barry Goldwater	[reply]
Re^3: Redundant regex ([0-9]{2} \| [0-9] {2, 4})? by ikegami (Patriarch) on Feb 27, 2009 at 01:35 UTC
Spaces removed, /`[0-9]{2}`/ does match a subset of what /`[0-9]{2,4}`/ matches. I'm sure what he wanted was just /`[0-9]{2,4}`/.	[reply] [d/l] [select]


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