I happened to have telephone numbers coming from ASN.1 encoded data translated into HEX (they're represented as BCD), but odd cyphers were swapped with even (e.g. "214365" instead of "123456"), so I found this trick quite useful.

It basically uses pack putting high nybble first, then unpack putting high nybble last to do the trick.

Note that it works only for HEX dumps, i.e. couples of octets in 0-9a-fA-F, so its usefulness is quite limited...

my $start = "214365";
my $final = unpack "h*", pack "H*", $start;

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In reply to Swapping odd-even characters of BCD hex data by polettix

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