@EXPREPLACE   Replaces text in an escaped string.

Syntax:
%@EXPREPLACE[from,to,flags,string]

fromthe substring to find and replace
tothe text which will replace from
flags1: case insensitive
2: replace only the first match
4: do not escapify the resulting string
stringthe string in which to find and replace text

Use commas to separate arguments. If you need a comma in any string, either enclose it in double quotes, or else use \c or \x002c to represent the comma. If you need a double quote, use \q or \x0022 to represent it.

All three string arguments — from, to, and string — may contain character escapes; they will be expanded before the search.

You can use the CESC_CHARS and CESC_FLAGS environment variables to tweak the way text is escapified.

echo %@expreplace[:),\U1f600,4,:):) Have a nice day! :):)]