perl -MO=Deparse -M"5;$S=shift;$R=shift;open $o,'>','new2.txt'" -ne "chomp;if($_=~/$S/){print qq/$_ $R?/;($_=$_)=~s/$S/$R/ if<STDIN>=~/y/}print$o $_.$/"
sub BEGIN {
    require 5;
    ()
}
$S = shift @ARGV;
$R = shift @ARGV;
open $o, '>', 'new2.txt';
LINE: while (defined($_ = readline ARGV)) {
    chomp $_;
    if ($_ =~ /$S/) {
        print "$_ $R?";
        ($_ = $_) =~ s/$S/$R/ if readline(STDIN) =~ /y/;
    }
    print $o $_ . $/;
}
-e syntax OK