#!/usr/bin/perl -l $_=pop;chop while print,s/.(?=(.))/chop($_=$&+$1)+$_/eg
#!/usr/bin/perl -l $_=pop;chop while print,s/.(?=(.))/chop($_=$&+$+)+$_/ge
#!/usr/bin/perl -l $_=pop;chop while print,s/(.)(?=(.))/chop($_=$1+$2)+$_/ge