$1 does not seem to work in the replacement.
because $1 from the m// is reset by the subsequent s///. You have to capture $1 in some variable: 
$_ =~ /<FN1>([^<].+)<\/FN1>/;
$found = $1;
$_ =~ s/<FN1ref>/<FN1>$found<\/FN1>/g;

[download]

--shmem 

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

In reply to Re: Find and replace using regex by shmem
in thread Find and replace using regex by rsriram

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