You only asked it to replace "sbo", not the whole line. I think you want 

s/^$group:.*/$newstring/;

[download]
or the clearer 
$_ = "$newstring\n" if /^$group:/;

[download]

I added ":" to the regex pattern so that you don't accidentally replace the group "sboadmin" (for example).

In reply to Re: How do I escape a :: in s///? by ikegami
in thread How do I escape a :: in s///? by xjlittle

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