Function symbol_at_cursor_with_source 

pub fn symbol_at_cursor_with_source(
    ast: &Node,
    offset: usize,
    current_pkg: &str,
    source_text: &str,
) -> Option<SymbolKey>

Extract a symbol key at a cursor offset with access to source text.

This variant is used by LSP handlers when additional source-aware disambiguation is needed (for example, barewords in use ... qw(...) lists).