^start of line
.*?any Unicode character (except for line terminators), repeated any number of times
\ba Unicode word boundary
protein_codingthe literal text protein_coding (case sensitive) \ba Unicode word boundary
.*?any Unicode character (except for line terminators), repeated any number of times
exonthe literal text exon (case sensitive) .*any Unicode character (except for line terminators), 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