$ perl -MData::Dumper -e 'q(abc de f abcdef) =~ m/(?<x>\w{3}).*\k<x>/ and print Dumper {%+};'
$ perl5.8.8 -MData::Dumper -e 'q(abc de f abcdef) =~ m/(?{$+{x} = pos})(\w{3})(?{$+{x} = substr($_, $+{x}, -$+{x}+pos)}).*(??{$+{x}})/ and print Dumper {%+};'