It's nothing to do with regexes and everything to do with lvalue substr. Taking a reference to substr doesn't create a new string, it just creates a special magical object with a pointer to the original string and the values of the substr arguments. When $xref is derefererenced, it triggers the magic which makes an actual string based on the values. Since you have $$xref in a loop, that causes a temporary copy of the substring to be made and thrown away 40,000 times.

Dave.

In reply to Re: Regex match is very slow against deref'd reference to substr/lvalue, is it normal? by dave_the_m
in thread Regex match is very slow against deref'd reference to substr/lvalue, is it normal? by Anonymous Monk

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