Aside from your regexes you will want to add a > to your second open or you will not be able to write to the file. For example:

open (FILE, ">blah.txt") or die;
print (FILE "1 blah\n2 blah\n3 blah\n") or warn "could not print";
close FILE;
open (FILE, "blah.txt") or die; # NOTE: no >
print (FILE "new data\n") or warn "could not print";
close FILE;
open (FILE, "<blah.txt") or die;
print <FILE>, "\n";
close FILE;

__OUTPUT__

could not print at temp.pl line 5.
1 blah
2 blah
3 blah
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flounder