Sorry, didn't notice that wrinkle the first time through. <TXT> needs to disappear - you are no longer using a file remember. I'd rework it to shift the lines out of the array bthus:

while (@data2) {
    $_ = shift @data2;

    if( m[/\*] ) {
        $_ .= shift @data2 until m[\*/] or ! @data2;
        s[ \s? / \* .+? \* / \s? ][]smgx; 
    }
}
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Note that the chomps are not required because they weren't added to the lines in the array. Note also the check for end of data in the until.