How it works
By default, the “Find” field is matched as plain literal text — a . means
a period, not “any character.” Turning on regex mode passes it straight to
JavaScript’s regular expression engine instead, so you can use patterns
like \d+ and reference capture groups in the replacement as $1, $2,
and so on.
Literal mode and the dollar sign
Outside of regex mode, a $ in the replacement is always inserted as a
literal dollar sign. It is never misread as a $1-style backreference,
even though those come from the same replacement syntax under the hood.
When to reach for regex mode
Plain find-and-replace covers fixed text. Regex mode is for patterns — replacing any run of digits, trimming a variable prefix, or reordering matched pieces with capture groups — the kind of edit a fixed string can’t express.