[Chicago-talk] \1 vs $1

[Andy_Bach at wiwb.uscourts.gov]

I just read a post:
> ... and \1 is deprecated for $1.

and having stumbled over this recently, I was a little suprised to hear of 
the deprecation.  What I'd found was \1 isn't the same as $1, in that
s/(.)\1//;

deletes duplicate chars, while;
s/(.)$1//;

depends upon the value of $1 - which, in this case'd be set *before* the 
subst got invoked!  On the right hand side, $1 is what we expect but \1 
also can change during the course of a regex evaluation - as the 
parser/matcher works, \1 will take on different values during backtracking 
etc - though, in the end \1 is the same as $1.

Er, am I all wet here?

a

Andy Bach, Sys. Mangler
Internet: andy_bach at wiwb.uscourts.gov 
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