Perl script grep - perl

Question

The script is printing the amount of input lines, I want it to print the amount of input lines that are present in another file
#!/usr/bin/perl -w
open("file", "text.txt");
#todd = <file>;
close "file";
while(<>){
if( grep( /^$_$/, #todd)){
#if( grep #todd, /^$_$/){
print $_;
}
print "\n";
}
if for example file contains
1
3
4
5
7
and the input file that will be read from contains
1
2
3
4
5
6
7
8
9
I would want it to print 1,3,4,5 and 7
but 1-9 are being printed instead
UPDATE******
This is my code now and I am getting this error
readline() on closed filehandle todd at ./may6test.pl line 3.
#!/usr/bin/perl -w
open("todd", "<text.txt");
#files = <todd>; #file looking into
close "todd";
while( my $line = <> ){
chomp $line;
if ( grep( /^$line$/, #files) ) {
print $_;
}
print "\n";
}
which makes no sense to me because I have this other script that is basically doing the same thing
#!/usr/bin/perl -w
open("file", "<text2.txt"); #
#file = <file>; #file looking into
close "file"; #
while(<>){
$temp = $_;
$temp =~ tr/|/\t/; #puts tab between name and id
my ($name, $number1, $number2) = split("\t", $temp);
if ( grep( /^$number1$/, #file) ) {
print $_;
}
}
print "\n";

Answer 1

OK, the problem here is - grep sets $_ too. So grep { $_ } #array will always give you every element in the array.
At a basic level - you need to:
while ( my $line = <> ) {
chomp $line;
if ( grep { /^$line$/ } #todd ) {
#do something
}
}
But I'd suggest instead that you might want to consider building a hash of your lines instead:
open( my $input, '<', "text.txt" ) or die $!;
my %in_todd = map { $_ => 1 } <$input>;
close $input;
while (<>) {
print if $in_todd{$_};
}
Note - you might want to watch for trailing linefeeds.