Be careful with greedy matches. You're doing

while ($content =~ m/(<textarea.*textarea>)/sg) {
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If your $content contains more than one textarea, this will match from the beginning of the first textarea to the end of the last one. That makes the /g fairly useless.

You probably want:

while ($content =~ m/(<textarea.*?textarea>)/sg) {
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Notice the *? non-greedy qualifier; that makes sure the first textarea> is matched.

Of course, this might not be the source of the problem you're asking about, but it is one possible problem with your code.
--
Mike