This came up here quite awhile back and at that time someone pointed out that alarm/sleep would not work in this context. During the regex execution they were suspended. I do not know if this is still the case as the regex engine got a pretty major overhaul since then and the internal details were beyond me at the time.

In reply to Re^4: how to restrict a regexp? by Your Mother
in thread how to restrict a regexp? by tfoertsch

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