Based on this answer from @kingkeith on the sublime text forum (thanks).
When using regular expressions to search within sublime text, flags can be specified by adding (?MY_FLAGS) at the beggining of the expression.
Example:
(?s)pattern with dots also matching new linesDefault flags can be removed by adding - before the flag letter:
(?-m)^pattern matching the whole file$The default flags are:
g: match more than once (cannot be removed)m:^and$match the beginning and end of lines, respectivelyi: depends on the case sensitive toggle state