You can match and edit substr: 
if (/^OBX(?:[^|]*|){2}([^^]*)/) {
    substr($_, $-[1], length($1)) =~ s/(?=([a-z]))/$1 > 'Z' ? 'L' : 'U
+'/ge;
}

[download]
Can't test it, so it might need some tweaking.
Caution: Contents may have been coded under pressure.

In reply to Re: Can anyone make this regex job neater? by Roy Johnson
in thread Can anyone make this regex job neater? by Melly

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