Both the 4-arg substr (I find left-side a confusing term) and s/// avoid copying, so should be more or less constant. They do this by just adjusting the beginning pointer into the string buffer and noting the offset used in the slot usually used for integer value. This is called the OOK hack (OOK being the flag set to indicate the integer slot is storing an offset).
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In reply to Re^2: Ways to delete start of string by ysth
in thread Ways to delete start of string by hsmyers

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