It was just that I was curious to see if such a task could be handled with a single regex, or whether my instinct to break the job into seperate regexes was correct.

I'm sure that some regex wizard may come up with a single regex to do it. If nothing else, you can always put some code into the replacement part of s/// and you can do other matches or substitutions in it. Whatever, it would be clumsy and unncessary...

Thanks to all for input - it looks like my original instinct was correct. Other solutions exist (of course - hey, it's perl), but split is inconvenient, since I'd need to rejoin later. Maybe it would be a little faster - I dunno - but (high) speed isn't really an issue with this particular job.

I really can't see why it should be "inconvenient": do you happen to work on some inner component of your car without unmounting it first? I suppose you do, instead, and then remount everything together when you're done, don't you? Here it's reasonable to break your string into chunks and operate on them, especially since

• you have to operate on the first one to decide whether to proceed with the rest or pass to the next line and
• you must do a substitution on the third one.

This is IMNSHO the cleanest WTDI.

All in all I would do it like thus:

#!/usr/bin/perl -lpi

use strict;
use warnings;

my @chunks=split /\|/;
next unless $chunks[0] eq 'OBX';
s/(?=[A-Z])/U/g,
  s/(?=[a-z])/L/g for $chunks[2];
$_=join '|', @chunks;

__END__
[download]

Note how simple and concise the effective code is.

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