It's probably easiest to just do it in the Perl script, e.g.
#!perl -l print '<flashlist>'; while (<>) { print '<listitem><flashtext>', $_, '</flashtext></listitem>'; } print '</flashlist>';
or, if you want the placeholders,
#!perl -l print '<${1:flashlist}>'; while (<>) { print '<${2:listitem}><${3:flashtext}>', $_, '</$3></$2>'; } print '</$1>';
Robin