Tip 87: Meet the Substitute Command

:[range]s[ubstitute]/{pattern}/{string}/[flags]

Tweak the Substitute Command Using Flags

# If you open the file in vim,
# then you can \"ayy@a the next line to execute the vim command: 
:h :s_flags

g flag makes the substitute command act globally, causing it to change all matches within a line rather than just changing the first one.
n flag suppresses the usual substitute behavior, causing the command to report the number of occurrences that would be affected if we ran the substitute command.
e flag silence these errors.
& flag simply tells Vim to reuse the same flags from the previous substitute command.

# If you open the file in vim,
# then you can \"ayy@a the next line to execute the vim command: 
:h sub-replace-special

Symbol	Represents
`\r`	Insert a carriage return
`\t`	Insert a tab character
`\\`	Insert a single backslash
`\1`	Insert the first submatch
`\2`	Insert the second submatch (and so on, up to `\9`)
`\0`	Insert the entire matched pattern
`&`	Insert the entire matched pattern
`~`	Use {string} from the previous invocation of `:substitute`
`\={Vim script}`	Evaluate {Vim script} expression; use result as replacement {string}