sub inRange { #return true if test value in range, undef otherwise
    my $toTest = shift; #the number to test
    my $ref2limits = shift; #get copy of limits argument ref

    if ($toTest >= $ref2limits->[0] and $toTest <= $ref2limits->[1]) {
        return 1;	#true/in range
    }
    else {
        return undef;
    }
}

my @limits = (1,999);	#upper and lower limit
if (inRange(123,\@limits)) {
    print "In range\n";
}
else {
    print "Outside limits\n";
}