nl add numbers suffix if regex match?

Question

If I have a text file saying this:

Xgrep () { something ; }  

Xgrep
Xgrep
Xgrep
Xgrep
Xgrep

I want it to look like this

Xgrep () { something ; }  

Xgrep 12
Xgrep 13
Xgrep 14
Xgrep 15
Xgrep 16

Meaning I want to choose at which number to begin, with suffixes instead of prefixes with one space between (-s " " for a space between). I thought that I could use nl for this, but reading the man page it doesn't seem so. I tried this:

nl -b pexpr=Xgrep -s " " ~/desktop/test.txt

However this just out put this:

    Xgrep
    Xgrep
    Xgrep
    Xgrep
    Xgrep

Which is probably because the regex syntax is wrong but I couldn't find a way for it to match, all other ways it just listed the usage.

This website is pretty much exactly what I am trying to do, but in command line form and only with numbers suffix.

Answer 1

% perl -ple 'BEGIN{$i=12} s/^(Xgrep)\s*$/"$1 ".$i++/e' < in
Xgrep () blah

Xgrep 12
Xgrep 13
Xgrep 14
Xgrep 15
Xgrep 16
Xgrep 17
% 

Print lines, BEGIN the counter, match Xgrep and tack the incremented number onto the end. Replace < in with filename and add -i flag to clobber file in-place, if desired. An awk solution will likely look very similar.