为什么此正则表达式不匹配？

Question

my $genlog_line_1= qr{
   \A
   (?:(\d{6}\s+\d{1,2}:\d\d:\d\d|\d{4}-\d{1,2}-\d{1,2}T\d\d:\d\d:\d\d\.\d+(?:Z|-?\d\d:\d\d)?))? # Timestamp
   \s+
   (?:\s*(\d+))                     # Thread ID
   \s
   (\w+)                            # Command
   \s+
   (.*)                             # Argument
   \Z
}xs;

my $line = "2018-12-14T17:32:52.236100+08:00        477637459 Query SELECT dv.mandatory,dv.optional FROM dbversion dv";

my ($ts, $thread_id, $cmd, $arg) = $line =~ m/$genlog_line_1/;

print $ts, $thread_id, $cmd, $arg;

Why does the regexp not match? What I expect is:

Timestamp 2018-12-14T17:32:52.236100
thread_id 477637459 
cmd Query 
arg  SELECT dv.mandatory,dv.optional FROM dbversion dv

Answer 1

You have +08:00 in your input, but -? in (?:Z|-?\\d\\d:\\d\\d)? only accounts for a negative value or values with no sign.

Thus, on the first regex line, you should replace -? with [+-]? to match an optional - or + . Also, since +08:00 part should not be part of Group 1, I suggest using a branch reset group , (?|...|...) , to capture different parts inside the group into the same group, Group 1:

(?|(\d{6}\s+\d{1,2}:\d\d:\d\d)|(\d{4}-\d{1,2}-\d{1,2}T\d\d:\d\d:\d\d\.\d+)(?:Z|[-+]?\d\d:\d\d)?)?
 ^^^                         ^ ^                                         ^     ^^^^         

Fixed pattern:

my $genlog_line_1= qr{
   \A
   (?|(\d{6}\s+\d{1,2}:\d\d:\d\d)|(\d{4}-\d{1,2}-\d{1,2}T\d\d:\d\d:\d\d\.\d+)(?:Z|[-+]?\d\d:\d\d)?)? # Timestamp
   \s+
   (?:\s*(\d+))                     # Thread ID
   \s
   (\w+)                            # Command
   \s+
   (.*)                             # Argument
   \Z
}xs;

See the regex demo .

Note the ? after the brach reset group might not be necessary if the TIMESTAMP is always present in the input.

Answer 2

The main problem of your regex is that it does not take into account the +08:00 present in your $line .

Change it in into:

\A(?:(\d{6}\s+\d{1,2}:\d\d:\d\d|\d{4}-\d{1,2}-\d{1,2}T\d\d:\d\d:\d\d\.\d+(?:Z|-?\d\d:\d\d)?))?(?:\+\d\d:\d\d)?\s+(?:\s*(\d+))\s+(\w+)\s+(.*)\Z

demo:

https://regex101.com/r/fgRCv1/3