I like to "correctly" handle the case where there may already be colons in the string. 
perl -E"$_=lc'02468ACE';s/[^:]{2}(?=[^:])\K/:/g;say"
02:46:8a:ce
perl -E"$_=lc'02:46:8A:CE';s/[^:]{2}(?=[^:])\K/:/g;say"
02:46:8a:ce

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In reply to Re^3: Script to convert HBA WWNs to lowercase and add ":" by samwyse
in thread Script to convert HBA WWNs to lowercase and add ":"[Updated] by perl514

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