I came up with something that seems to work - using an eval to evaluate a string containing the regular expression variable...

FEOUTER: while ($tkey = each(%targf)) {
        # Apply Search and Exception to each log line
        $found = 0;
        foreach $scline (@$srch_except) {
            # Split string intonext FEOUTER; qualifier and text
            $ttype = substr($scline, 0, 1);
            $ttext = substr($scline, 1);
            $eval_cd = "\"$tkey\" =~ $ttext";

            if ($ttype eq '!') {
                if (eval "$eval_cd") {
                    $targf{$tkey} = "1:0";
                    next FEOUTER;
                }
            }
            elsif ($ttype eq '&') {
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