> cat 714766.pl
#!/usr/bin/env perl

use strict;
use warnings;
use Data::Dumper;
use Getopt::Std;

#print 'ARGV ',Dumper(\@ARGV);

my $test = 1;

my %opt;
getopt('st',\%opt);
#print 'opt ',Dumper(\%opt);

if ($opt{'t'}) {
    $test = 1; ## testing
    #print "set test=1 again\n";
} elsif ($opt{'s'}) {
    $test = 0; ## not testing
    #print "set test=0\n";
}
#print "test=$test\n";

if ( (!(defined($opt{'s'}))) && (!(defined($opt{'t'}))) ) {
    print "neither -t or -s used\n";
}
else {
    print "either -t or -s used\n";
}