You're matching .* for no good reason. And you're using a my $x in an if statement in a potentially dangerous way. I'd rewrite your code as:

for (reverse <file_name.*>) {
  my $old = $_;
  next unless s/\.([0-6])$/'.' . (1 + $1)/e;
  rename $old => $_;
}
[download]

This kills a dozen birds with one stone. I do the substitution, instead of trying to match and then substituting. One of my regex red flags is the m/foo/ and s/foo/bar/ construct -- it's redundant. Also, I make the RHS (right-hand side) of the s/// code to be evaluated by using the /e modifier.

_____________________________________________________
Jeff japhy Pinyan: Perl, regex, and perl hacker.
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;