C:\>perl -MO=Deparse -pl -e "next if /bala/;s/([^:]+)([^:]+)/$2$1/" file.txt
BEGIN { $/ = "\n"; $\ = "\n"; }
LINE: while (defined($_ = <ARGV>)) {
    chomp $_;
    next if /bala/;
    s/([^:]+)([^:]+)/$2$1/;
}
continue {
    print $_;
}
-e syntax OK