use strict;
my $R;
my $i=1;

sub mySub {
    printf "\n\n%d. R = \"%s\"\n",$i++,$R;
    unless ($R) {
        print "CONDITION WORKS\n";
        $R = 'some string';
    }
}

print mySub(); #prints CONDITION WORKS\nsome string
print mySub(); #prints some string
print mySub(); #again