a;b;1;foo
j;k;2;dog
m;n;3;cat
y;z;1;bar

##</code><code>##

#!/usr/bin/perl -w

use strict;
use warnings;

my @rows = `awk -F';' '\$3==1' file.csv`;
my $lines= join('', @rows );
print "string: $lines";
exit;

##</code><code>##

$ ./at.pl 
string: a;b;1;foo
y;z;1;bar
$