\X fixes the utf8 problem, but there's still a problem with this regex...

#!/usr/bin/perl -w
use strict;
use utf8;

my($a,$b,$c);
$a=$b=$c="123\n456\n";

print chop $a;       # prints "\n"
print $b =~ s/\X$//; # prints "1"

print $a;            # prints "123\n456"
print $b;            # prints "123\n45\n"  ## OOPS!!!
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i believe s/\X\z// will do what you want, although it still won't return the character removed. instead, use substr EXPR,OFFSET,LEN,REPLACEMENT (i.e. substr $_,-1,1,'').

~Particle *accelerates*