It seems like the second pattern does not really contain any class. I tried it in Perl (5.18) on my Windows machine and the only thing that matches that second pattern was the string "[a-z]0-9]". And frankly, I did not expect otherwise!
Basically using '\x5b' should be similar to using '\[', meaning that you want the actual '[' character rather than the special '[' meta-character. I may be wrong but I recall that this is how it was explained in the regex school.
Ze'ev Atlas
________________________________
From: "Jim_Dailey@???" <Jim_Dailey@???>
To: pcre-dev@???
Sent: Thursday, September 18, 2014 11:05 AM
Subject: [pcre-dev] Treatment of \x5b and \x5d
I ran across something strange, and wondered if this is expected.
In the transcript below, the 2 REs do not behave the same. The
intent of the REs is to match 1 or more characters in a class
consisting of decimal digits, lower case letters, and the closing
square bracket (']').
The two REs are: "[a-z\x5d0-9]+" and "\x5ba-z\x5d0-9]+" (the '['
starting the first RE is replaced by '\x5b' in the second RE).
The first RE works as expected, but the second RE that begins with
'\x5b' does not; the character class in the second RE is terminated
by the '\x5d', but that is not the case in the first RE!
If it is expected, can someone explain the logic behind how these
escape sequences are supposed to work?
Thanks,
Jim
---
C:\Users\JimD\Downloads\pcretest\bin>pcretest -b
PCRE version 7.0 18-Dec-2006
re> "[a-z\x5d0-9]+"
------------------------------------------------------------------
0 37 Bra 0
3 [0-9\]a-z]+
37 37 Ket
40 End
------------------------------------------------------------------
data> "AA a02]23 "
0: a02]23
data> ^Z
C:\Users\JimD\Downloads\pcretest\bin>pcretest -b
PCRE version 7.0 18-Dec-2006
re> "\x5ba-z\x5d0-9]+"
------------------------------------------------------------------
0 21 Bra 0
3 [a-z]0-9
19 ]+
21 21 Ket
24 End
------------------------------------------------------------------
data> "AA a02]23 "
No match
data> ^Z
C:\Users\JimD\Downloads\pcretest\bin>
--
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