The SUBSTITUTE NEXT (abbreviated N) command replaces the next occurrence
 of string-1 with string-2.

 Format: [SUBSTITUTE] NEXT [/string-1/string-2/]

 The search for string-1 is made forward from the current location. When
 a substitution is made, the line where the substitution occurs becomes
 the current line.  When the optional strings are omitted, the strings
 used in the last SUBSTITUTE or SUBSTITUTE NEXT command are used.