You search for a backslash in the second alternative, that should be a forward slash. Anyway, that latter alternative is useless, as the former one will match it too. And like castaway said, you're suffering from regexp greediness.

Your remaining problems are:

1. A tag can contain "<" or ">" characters in quoted attributes
2. a tag can contain a newline. Why read line by line anyway?

To solve the first problem, you could try the next:

s/<(?>[^>'"]+|"[^"]*"|'[^']*')*>//g;
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Try it with

$_ = '<foo attr="heh>hoh">bar</foo>';
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As for the second problem, processing the whole file in one go while adding the /s modifier, would probably help.