if (101 .. 200) { print; }  # print 2nd hundred lines
next line if (1 .. /^$/);   # skip header lines
s/^/> / if (/^$/ .. eof()); # quote body

# parse mail messages
while (<>) {
    $in_header =   1  .. /^$/;
    $in_body   = /^$/ .. eof();
    # do something based on those
    } continue {
        close ARGV if eof;              # reset $. each file
}