my $flag = 1;
if ( -e $file1 ) { 
print "Script '$file1' already exists\n";
open(FILE1,"$file1");
my @seq1 = <FILE1>;	
close FILE1;
# @seq2 contains the contents of the file to generated.
my $diff = Algorithm::Diff->new( \@seq1, \@seq2 );
my $sep;
my $flag = 1;

$diff->Base( 1 );   # Return line numbers, not indices
while(  $diff->Next()  ) {
next  if $diff->Same();
if(  ! $diff->Items(2) || ! $diff->Items(1) ) {
$flag = 0;
print $diff->Get(qw( Min1 Max1 Max2 )),"\n";
} 
else {
$flag = 0;
$sep = "---\n";
print  $diff->Get(qw( Min1 Max1 Min2 Max2 )),"\n";
}
 print "< $_"   for  $diff->Items(1);
 print $sep;
print "> $_"   for  $diff->Items(2);
}

if($flag == 0) {
print
"User edits,do u want to overwrite the exisiting $file1?";
print "[INFO] Continue ? [no]";
my $answer = <STDIN> ; chomp $answer;
if ($answer =~ /^n/i) {
  print"Not Generated the script '$file1'";
}
....