the compiler thinks that $next_word[$BEL_LETTERS] is member $BEL_LETTERS of array @next_word.

Use ${nextword}[$BEL_LETTERS]. It's documented in perldata, search for "there is an unfortunate ambiguity".

--
David Serrano

In reply to Re: variables in regex character classes by Hue-Bond
in thread variables in regex character classes by amir_e_a

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