my $re = shift or die "re expected\n";
    while (<>) {
        chomp;
        my ($field, $value) = ($_ =~ $re);
        print "'$_' -> ('$field', '$value')\n";
    }

##</code><code>##

 'a:b:c' -> ('a', 'b:c')
 'a\:b:c' -> ('a\:b', 'c')
 'a\\:b:c' -> ('a\\', 'b:c')
 'a\\\:b:c' -> ('a\\\:b', 'c')
 'a:' -> ('a', '')
 ':b' -> ('', 'b')

##</code><code>##

 
 'a\:b' -> ('', 'b')

##</code><code>##

 ^((?:[^:\\]+|\\.)*):(.*)