Search over source code by typing a regular expression into the query box. Searches are case-insensitive by default:

hello,?\sworld try it

Queries containing capital letters are matched case-sensitively:

Hello try it

Use case: to force a lower-case match:

case:hello try it

Use lit: to match a literal string. At present you can't mix and match a literal string and a regular expression.

lit:()() try it

Restrict matches to specific files using a file: modifier:

exit file:\.c$ try it

Wrap a clause in parentheses to stop interpretation of spaces or query modifiers:

(file:) try it

Exclude files from matches using -file::

exit -file:\.c try it

The complete RE2 Syntax reference is available on their wiki page: