Strings don't increment this way, if what you are trying to do is take

$alias = "johnq.smith1";
$alias++;
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and turn $alias into

"johnq.smith2"
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. What you'll need to do is save the digits into a temporary variable, increment them, then append to the digitless string:

$alias = "johnq.smith1";

if ($alias =~ s/(\d+$)//) {
  $alias .= $1++;
  # $alias is now "johnq.smith2"
}
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There are, of course, other ways to achieve this, but not via directly incrementing a string.

Update: Ignore my response. Of course you can increment strings this way. Is it friday yet?