use strict;
use warnings;

while(<DATA>) {
    $_ =~ s/(\D*)(\d*)(\D*)(\d*)/$3$2$4$1/g;
    print $_;
}

__DATA__
AAAAAAAAAA1111BBBBBB222222
BBBBBBBBBB2222CCCCCC333333
CCCCCCCCCC3333DDDDDD444444