my @valid= 1..5;
my %valid= map { $_=>1 } @valid;
# ...
$valid{$b} or 
  print "\$b has to be one of ",
        join(", ",@valid[0..$#valid-1]),
        " or $valid[-1]\n";
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The reason I like this solution the best (out of all the above, perhaps except /^[1-5]\z/) is that it's practical for values, even a large number of them, that aren't sequential.

-Paul

This one gets my vote as well. Creating a hash to do the job is expressive, readable and general. Also helps you avoid hardcoding in the (1..5) values, letting you put them at the top where constants generally belong. demerphq++

~dewey

if ($b=~/^[1-5]$/) {
    print "\$b has to be a number and is either 1, 2, 3, 4, or 5.\n";
    }
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The correct regex solution :)

/^[1-5]\z/
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To say that using "\z" is "the correct regex solution" (and imply that using "$" is "incorrect") is a bit silly, esp. in the absence of more detailed info regarding the application.

There are some situations where the two solutions will have different behaviors, and in such cases, it's up to the programmer to decide which is more appropriate. Either one could be more useful (or "correct") than the other, depending on the task. But in many common situations, they behave the same, and neither is "more correct" than the other.

if ($b == 1 || $b == 2 || $b == 3 || $b == 4 || $b == 5) {
   print "\$b is a number and is either 1, 2, 3, 4, or 5.";
} else {
   print "\$b has to be a number and to be either 1, 2, 3, 4, or 5.";
}
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I'd write

if ($b =~ /^\d$/ and $b > 0 and $b < 6) {
    ...
}
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_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

If you can't use the character set [1-5] in the regex, at least use the actual constants for comparison rather then a different bunch:

if ($b =~ /^\d$/ and $b >= 1 and $b <= 5) {
    ...
}
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---

DWIM is Perl's answer to Gödel

if ($b == any(1, 2, 3, 4, 5)) {
 print "\$b has to be a number and is either 1, 2, 3, 4, or 5.";
}
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if (length($b)== 1 && $b >= 1 && $b <= 5) {
   print "\$b has to be a number and is either 1, 2, 3, 4, or 5.";
}
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no warnings qw(uninitialized numeric);
print "\$x is a number ($x) is either 1, 2, 3, 4, or 5.\n"
  if grep {$x == $_} (1 .. 5);
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print "\$b has to be a number and is either 1, 2, 3, 4, or 5." if ($b 
+< 1 || $b > 5);
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Take a look at perlintro. It has good explenations of all the constructs

Since an input validation is not likely to be a big user of system resources, an "optimal" solution is one that's easy to read and easy to change.

If the value is being used for something which could be character-based, such as a menu selection, use a hash, as suggested by demerphq. If it's going to be used for something that will be strictly numeric, I would just do something like this:

use strict;
use warnings;

my $entered_value;

my $min_allowed = 1;
my $max_allowed = 5;

if($entered_value =~ /^\d+\z/s and
   ($entered_value >= $min_allowed and $entered_value <= $max_allowed)
+)
   {
    do_magical_processing($entered_value);
    }
else{
    print "value must be a number no less than $min_value and not grea
+ter than $max_value\n";
}
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If he is looking for the quicker way. Would a regex really be the best solution?

If he's looking for the quickest way to that thing, then he's most probably micro-optimizing, which is most probably not good. But AIUI he's rather searching for a slightly less clumsy solution than his own.

for (1..5) {
   $_ == $b ? goto JUMP : 0;
}
print "\$b has to be a number and is either 1, 2, 3, 4, or 5.";
JUMP:
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just another way around... just choose the best (comfortable) for you.

for (1..5) {
   $_ == $b ? goto JUMP : 0;
}
print "\$b has to be a number and is either 1, 2, 3, 4, or 5.";
JUMP:
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Please do not make me repent of having mentioned goto to you!!

Also, I'm fully aware of your obsession for ?: (in fact I even frontpaged that other thread, since after all a nice discussion got out of it) but then again there's no need to use it there: it's plain ugly. Do you really want to stay concise? Just use a short circuiting and:

$_ == $b and goto JUMP for 1..5;
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But really: do not use goto at all, and adopt some of the other solutions others suggested, instead.

using goto won't hurt you when you just use it once... and the distance of goto and the refering label name should be as much as possible close to each other so you can keep an eye on that.

Using goto will hurt you even when you just use it once... because then you will want to use it twice, then three times and so on. And first or later you will want to insert some code between a goto and its target, because "that's not much code". And then some more, because that's still not too much", and so on. And first or later it will bite you back in the neck. And even without that, quite a lot of programmers will think you're an asshole anyway. Of course you can live with that, but... I wouldn't: there's a good reason why they would.