Wrong syntax for backward non-match

[ghost]

Wrong:

:1M/G(?<=O)
E486: Pattern not found: G\%(O\)\@<=

Correct:

\%(O\)\@<=G

[othree]

If you are looking for a ahead(right) zero-width match. You should use (?=pattern). 'G(?=O)' match:

GO
^

If you are looking behind(left) You should change the order of your pattern to (?<=O)G This match 'G' follows 'O'

OG
 ^

ref: perlre

[ghost]

:-O Thanks!