I use this template to convert uri: identifiers to gutenberg: ones.
Code:
program:
publisher = $publisher;
ids = $identifiers;
u = select(ids, 'uri');
g = select(ids, 'gutenberg');
if
publisher == 'Project Gutenberg'
&& u != g
then
n = re(u, '^http://www.gutenberg.org/(\d+)', '\1');
ids = list_union(ids, strcat('gutenberg:', n), ',')
fi;
if
publisher == 'Project Gutenberg'
&& u
&& g
then
ids = list_difference(ids, strcat('uri:', u), ',')
fi;
ids
To use this, get the
Action Chains plugin and make a chain that applies a single-field template edit to the identifier field.
If you prefer different identifier, change 'gutenberg' in lines 5 and 12. You can also change the checks in line 8 and 16 to something like
'Gutenberg' inlist $tags.