I love $., specially because it works so well with the scalar form of the .. operator. For example, to extract the subroutines of a script and label the lines with linenumbers one could use this:

$ cat test2.pl
#!/usr/bin/perl

my $god;

sub test {
     my ($param) = @_;
     print $param;
     return
}
__END__

$ cat test.pl | perl -ne 'print "$. $_" if /^sub/ .. /[}]/'
5 sub test {
6      my ($param) = @_;
7      print $param;
8      return
9 }
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