VIM skills

Merge multiple blank lines

:%s/^\_s\+\n/\r/g

Note: \_s match white space and blank lines

Grep by unicode character

# replace back slash(\) to front slash(/)
:%s#\%x5C#/#g

:help regexp for details about some specific syntax to select unicode characters with a regular expression in Vim.

|/\%d|  \%d \%d match specified decimal character (eg \%d123)
|/\%x|  \%x \%x match specified hex character (eg \%x2a)
|/\%o|  \%o \%o match specified octal character (eg \%o040)
|/\%u|  \%u \%u match specified multibyte character (eg \%u20ac)
|/\%U|  \%U \%U match specified large multibyte character (eg \%U12345678)