2 added 9 characters in body
source | link

Perl, 1919 18 characters

perl -pe 's/(.)(\d.)/$1x$2/ge'

The rules for counting switches on the command-line are here.

Perl, 19 characters

perl -pe 's/(.)(\d)/$1x$2/ge'

The rules for counting switches on the command-line are here.

Perl, 19 18 characters

perl -pe 's/(.)(.)/$1x$2/ge'

The rules for counting switches on the command-line are here.

1
source | link

Perl, 19 characters

perl -pe 's/(.)(\d)/$1x$2/ge'

The rules for counting switches on the command-line are here.