Svncopy.pl problem pinning new externals formats

I am migrating my repos to svn 1.6.17 and i'd like to change the format of the property svn:externals to the new ones supported from 1.6 version.

The problem is that if I change the externals to the new supported formats, svncopy.pl stops working. I have seen that this script only works with the old format, therefore I modified the method UpdateExternalsOnDir (see the attached file, svncopy.modified.pl.in). But after doing that, svncopy is not able to get the latest revision. E.g. svn:externals = ^/tools/calc/trunk calc.

Can anybody help me?

Thanks,
Darío.