Here is the error:
a> line 1.
Use of uninitialized value $fields[1] in numeric gt (>) at tab.pl line 19, <$tabdata> line 2.
Use of uninitialized value $fields[1] in numeric gt (>) at tab.pl line 19, <$tabdata> line 3.
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Use of uninitialized value $fields[1] in numeric gt (>) at tab.pl line 19, <$tabdata> line 21.