$_ =~ s/(\d+)/sprintf("%03d",$1)/e;

##</code><code>##

    s/(\d+)/sprintf("%03d",$1)/e;

##</code><code>##

    (my $newname=$_) =~ s/(\d+)/sprintf("%03d",$1)/e;

##</code><code>##

    rename($oldname,$_) unless $oldname eq $_;

##</code><code>##

touch zizze; perl -le 'rename "zizze", "zizze" or die $!'