If means that your $mappingfield variable contains a value with the regex quantifier metacharacter '*' at the beginning - infact it appears that the variable only contains '**'. This is the same form of message you get if you do:

 perl -e'$foo='babab'; $foo =~ /*aba*/'
Quantifier follows nothing in regex; marked by <-- HERE in m/* <-- HER
+E aba*/ at -e line 1.
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If you intend to use metacharacters in the $mapping field then you should either use quotemeta prior to interpolating it into the pattern or shoould use \Q directive to suppress the interpretation of the metacharacters in the expression.

/J\