rdfield is right on the money.

Pay attention to exactly what error message are trying to tell you - they are usually pretty easy to understand if you take a minute and really look at it. Notice

   Use of uninitialized value in numeric eq (==) at
   Creating_table_D.pl line 31.

   Use of uninitialized value in numeric eq (==) at
   Creating_table_D.pl line 35.
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   sub create_table ($) {

     my($schema_in) = $_;

     if ($schema_in == "1"){ # offending line 1
       my @tables = qw/A/;
     }

     if ($schema_in == "2"){# offending line 2
       my @tables = qw/A B C/;
     }
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Notice in particular Use of uninitialized value. This probably means that $schema_in has *NO* value. As rdfield suggested, do some debugging - print out the value of $schema_in in subroutine 'create_table' to see if it is receiving the value you think it's receiving.

Notice another thing - when doing a numeric comparison, you don't want to test using *string* "1" - you want to test using number 1 - without quotes around it. If you include the quotes and $schema_in contains a number, then perl will have to convert the string to a number and then do the numeric comparison.

HTH.