The manual states that

 

"the empty regular expression ‘//’ repeats the last regular expression match"

 

however this does not work when the empty regex follows a 2-address of the form LINE_NUMBER,/REGEX/

e.g.

 

# printf %s\\n {1..5} | sed '2,/5/{//!d}'

 

 

"sed: -e expression #1, char 0: no previous regular expression"

 

instead of printing

 

1

5

 

If it matters, a 2-address like /REGEX/,LINE_NUMBER works as expected e.g.:

 

# printf %s\\n {1..5} | sed '/2/,5{//!d}'

 

correctly prints

 

1

2

 

This is with gnu sed 4.4 on archlinux, vanilla.