modify word split.
symbolword-mode determine word split for symbol.
for instance hyphen.

Key     Word oriented command      Symbolword oriented command
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M-f     `forward-word'             `symbolword-forward'
M-b     `backward-word'            `symbolword-backward'
M-d     `kill-word'                `symbolword-kill'
M-DEL   `backward-kill-word'       `symbolword-backward-kill'