<much handwaving> If you want to match ANY of the characters in $BEL_LETTERS, and $next_word is a literal string (and not a "true regex" which should be interpreted with meta characters like *) you should probably do something like 

my $BEL_LETTERS = qr/[ABVHD]*/;

[download]
and 
 s/\b(\Q$next_word\E$BEL_LETTERS)\b/>$1</gi);

[download]
</much handwaving> Good luck :-)
"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: variables in regex character classes by Joost
in thread variables in regex character classes by amir_e_a

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