split the problem: first get the string, then condense it. Assuming you can't use any of te std XML/HTML modules to get the text, you could try: 
sub condense { $_[0] =~ s/\s+/ /g }
$in =~ s/(<tag>)(.*?)(<\/tag>)/ $1 . condense($2) . $3 /ge;

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--Dave

In reply to Re: taking white space out between closing and opening tags by dpuu
in thread taking white space out between closing and opening tags by chuleto1

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