perl -MData::Dumper -e '$_=q[a 2 b 4,5,6 c d e 45,657,-67];@arr=split /\s+/;do { $arr[$_]!~/\d+/ and splice(@arr,$_,0,[]) } for grep {($_%2)} 0 .. $#arr;(%hash)=@arr;print Dumper(\%hash)'