I would have done it like that :

undef $/; # to absorb the whole file in a single read.
open FILE, $filename;
$all = <FILE>;

$all =~ s/\.html/\.asp/g; # this will substitue the .html to .asp glob
+ally

# this takes the part in between the body tags...

$all =~ s{^.*?\<body.*?\>(.*)\</body.*?\>.*?$}
     {$1}isx;

print OUTFILE $all;

close FILE;
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