Reading the file into an array might be a big mistake, instead, use the in-place editing: 
local ($^I,@ARGV)=('.bak','file.html');
my $p=1;
while(<>){
$p-- if /<\/tr>/;
print "Add this line\n" if $p==-4
print if $p;
$p-- if /<tr>/;
}

[download]
You can read more about in-place editing in perlvar($^I) and perlrun(-i).

In reply to Re: How to delete and add line in the middle of a file? by Ido
in thread How to delete and add line in the middle of a file? by Anonymous Monk

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