PERL TESTING Print only ok/not ok

commandline session

$cat test5.pl
#!/usr/bin/perl
use strict;
use warnings;

my $result;

$result = `/usr/bin/concalc 1  + 1`;
print $result;
if ( $result == 1 ) {
    print "okn";
}
else {
    print "not okn";
}

$result = `/usr/bin/concalc 2 + 2`;
if ( $result == 4 ) {
    print "okn";
}
else {
    print "not okn";
}

$result = `/usr/bin/concalc 2 + 2 + 2`;
if ( $result == 6 ) {
    print "okn";
}
else {
    print "not okn";
}



$perl test5.pl
tcsetattr fehler: Invalid argument
tcsetattr error: Invalid argument
2
not ok
tcsetattr fehler: Invalid argument
tcsetattr error: Invalid argument
ok
tcsetattr fehler: Invalid argument
tcsetattr error: Invalid argument
ok
$