Maybe this wasn't part of your original question, but your more complete posting of code contains some things you ought to fix. In particular, this condition has a couple problems:

if (($site =~ "l",) || ($site =~ "c") || ($site =~ "n")
      || ($site =~ "w"))
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Apart from the extra comma, the use of the "=~" operator with literal strings seems wrong here; the intention was either this:
if ( $site =~ /[lcnw]/ )
or this:

if ( $site eq "l" or $site eq "c" or $site eq "n" 
     or $site eq "w")
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which could (should) be stated this way:
 if ($site =~ /^[lcnw]$/)

The other problem is that, as written, it actually acts like the first alternative, which means that it will match when $site contains "wf", and as a result, the subsequent condition will never get a chance to work:

elsif ($site =~ /wf/)
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Also, you are repeating the same statements in these three successive conditional blocks.

If you really want "$site" values containing "wf" and "h" to remain unchanged, while other "$site" values (that might contain a "w") get changed to "l" -- and in all other respects these cases get the same treatment -- do it this way (assuming that "$site" should be a single letter or "wf" only):

if ($site =~ /^([lcnh]|wf)$/) { # one block handles all cases
    $site = "l" unless ( $site =~ /(h|wf)/ );
    $server = "yos.$site.com";
    # and so on
}
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