in reply to Best way to put : between fields in a string

Uhmmm, you're not giving the exact rules of the transformation, so I feel authorized to suggest Knuth's solution: 
   print "A3:xyz45:M98:AB7:Z9";  # :)

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Update: added link.

Flavio (perl -e "print(scalar(reverse('ti.xittelop@oivalf')))")

Don't fool yourself.

In Section Seekers of Perl Wisdom