You should have a look at the HTML::Strip module, it does a good job at stripping HTML tags.

As for your immediate problem...

my $str = do { local $/; <DATA> };

$str =~ s!<(script|style|option|textarea)[^>]*?>.*?</\1[^>]*?>!!gsi;

# In fact when you turn on the non-greedy match with '?', you
# don't need the [^>] either... So the following regex works
# equally well:

# $str =~ s!<(script|style|option|textarea).*?>.*?</\1.*?>!!gsi;

print "$str\n";

__DATA__
<script>
This is removed.
</script>
This is not removed.
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