Others already gave you good suggestions as to how to do what you want. I feel like adding a few random observations:

sub setManagers() {

        my $getInputFlag = 1;
        my $writeFileFlag = 1;
        my $mCounter = 0;
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This may be a spurious comment, but in my experience I found that in Perl you seldom need flag variables like that. Not to say that this is "wrong", but sounds suspect...

        my $ans = &promptUser("Do you wish to configure SNMP Managers 
+on $var? ", "yes");
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In modern perls you most often do not want to adopt the & form of sub call unless you really know what you're doing, which doesn't appear to be the case here...

        if ($ans =~ /^[n]o?/i) {
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[n]?

          if ($address =~ /^(([3-9]\d?|[01]\d{0,2}|2\d?|2[0-4]\d|25[0-
+5])\.){3}([3-9]\d?|[01]\d{0,2}|2\d?|2[0-4]\d|25[0-5])$/)
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Here your regex has the form ^(?:/$regex\.){3}/$regex$, so you could increase its readability porting it explicitly into that form. Also, here you have parens for grouping (an alternation), but they're capturing parens, so you may change them into

(?:[3-9]\d?|[01]\d{0,2}|2\d?|2[0-4]\d|25[0-5])
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instead.

All in all I'd use an appearently more complex, but IMHO more readable test possibly putting it into a sub. I'd split on /\./\, then check that the return list has four elements, and do a check on each of them. This seems more {portable,maintainable}, especially if -like it seems reasonable- each of them would require a separate range of validity.

                $managers[$mCounter]{address} = $address;
                $managers[$mCounter]{port} = $port;
                $managers[$mCounter]{version} = $version;
                $managers[$mCounter]{community} = $community;
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Also:

@{ $managers[$mCounter] }[qw/address port version community]=
  ($address $port $version $community);
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But then I wouldn't probably create the intermediate variables at all, if you ask me...

                my $numOfManagers = scalar(@managers);

                print FILE "manager.total=$numOfManagers\n";

                for (my $i=0; $i<$numOfManagers; $i++) {
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scalar is pleonastic there, and a rule of thumb is that Perl-style for loops should always be preferred over C-style ones, if they're equivalent, i.e. if the latter doesn't buy you something special, which definitely is not the case here. Thus:

for my $i (0..$#managers) { ... }
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But then chances are that doing some modification in the logic above you may just turn it into

for my $item (@managers) { ... }
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