maybe 
 DB<20> print join " ", reverse split /(..)/ , sprintf "%06x\n", 2*10*
+*$_ for 0..5

02  00  00
14  00  00
c8  00  00
d0  07  00
20  4e  00
40  0d  03
 DB<21>

[download]

I'm not sure why you want low bytes first, but please note you had trailing 00s in your example too.

update

this will give you the number of necessary bytes 

  DB<29> say 1+int (log (2*10**$_)/log 256)  for 0..5
1
1
1
2
2
3

[download]

Cheers Rolf
(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery

In reply to Re: Split any number into string of 8-bit hex values (=1 byte) by LanX
in thread Split any number into string of 8-bit hex values (=1 byte) by drsweety

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