What about the -i($^I)?

{local($^I,@ARGV)=('.bak','file.txt');
while(<>){
#the current line is now in $_, the line in the new edited file is wha
+t ever I will print now(to ARGVOUT which is already select()ed)
if ($.==$linenumberiwanttochange){
chomp;
#edit the line
print "$_\n"; #print the edited line
}else{print} #leave the other lines with no change
}
}
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