^start of line
\s*any whitespace character, repeated any number of times
\{the literal { (12310 / 1738 / 7B16)
\/the literal / (4710 / 578 / 2F16)
\*the literal * (4210 / 528 / 2A16)
DELETE}the literal text DELETE} (case sensitive) Group 1(\s*(?:\r?\n(?!\s*\{(?:\/\*DELETE|DELETE\*\/)}).*)*) \s*any whitespace character, repeated any number of times
Non-Capturing Group(?:\r?\n(?!\s*\{(?:\/\*DELETE|DELETE\*\/)}).*)* *repeats the group contents below any number of times:
\r?optionally matches a carriage return (ASCII 13)
\na line-feed (newline) character (ASCII 10)
Negative Lookahead(?!\s*\{(?:\/\*DELETE|DELETE\*\/)}) \s*any whitespace character, repeated any number of times
\{the literal { (12310 / 1738 / 7B16)
Non-Capturing Group(?:\/\*DELETE|DELETE\*\/) 1st Alternative\/\*DELETE \/the literal / (4710 / 578 / 2F16)
\*the literal * (4210 / 528 / 2A16)
DELETEthe literal text DELETE (case sensitive) 2nd AlternativeDELETE\*\/ DELETEthe literal text DELETE (case sensitive) \*the literal * (4210 / 528 / 2A16)
\/the literal / (4710 / 578 / 2F16)
}the literal } (12510 / 1758 / 7D16)
.*any character (except for line terminators), repeated any number of times
\r?optionally matches a carriage return (ASCII 13)
\na line-feed (newline) character (ASCII 10)
\s*any whitespace character, repeated any number of times
\{the literal { (12310 / 1738 / 7B16)
DELETEthe literal text DELETE (case sensitive) \*the literal * (4210 / 528 / 2A16)
\/the literal / (4710 / 578 / 2F16)
}the literal } (12510 / 1758 / 7D16)
\s*any whitespace character, repeated any number of times
$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