^start of line
Group 1([[:alnum:]_]+[[:space:]]){1,5} {1,5}repeats the group contents below between 1 and 5 times:
Character Class[[:alnum:]_]+ +matches at least one character from the set below:
[:alnum:]an alphanumeric character [a-zA-Z0-9]
_the literal _ (9510 / 1378 / 5F16)
Character Class[[:space:]] [:space:]a whitespace character, including a line break [ \t\r\n\v\f]
\(the literal ( (4010 / 508 / 2816)
Group 2((/[[:alpha:]]+)+\.[[:alpha:]]) +repeats the group contents below at least once:
/the literal / (4710 / 578 / 2F16)
Character Class[[:alpha:]]+ +matches at least one character from the set below:
[:alpha:]an alphabetic character [a-zA-Z]
\.the literal . (4610 / 568 / 2E16)
Character Class[[:alpha:]] [:alpha:]an alphabetic character [a-zA-Z]
:the literal : (5810 / 728 / 3A16)
Character Class[[:digit:]]+ +matches at least one character from the set below:
[:digit:]a digit [0-9]
\)the literal ) (4110 / 518 / 2916)
\.the literal . (4610 / 568 / 2E16)
$end of line
g modifier: global. Finds all matches instead of stopping after the first
m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string