in reply to Recursive substitution difficulties

s{(<name>.*?</name>)<value>(.*?)</value>}{ $1 . join '', map "<value>$_</value>", split /\|/, $2 }seg;

Better version for 5.10+:

s{<name>.*?</name>\K<value>(.*?)</value>}{ join '', map "<value>$_</value>", split /\|/, $1 }seg;

Update: Oops, didn't pay enough attn to the desired output.