No, all regex get compiled into regex opcodes. If they contain no variables, they are compiled once at Perl compile-time. If they contain variables, then the /o flag controls whether the compilation happens the first time it is seen at runtime, or every time it is seen at runtime. But the compilation always happens. It must happen... you can't interpret a regex "directly".

Also note that some modern innovations make /o somewhat less nasty. The regex engine maintains a one-level cache, so if the regex to be compiled hasn't changed and was the most recent one compiled, the cached compilation is reused. That means you don't need /o for this: 

my @winners = grep /prefix$part/, @list;

[download]
In older Perls, that regex would have been recompiled for each element of @list. Not so, now. Even works for stuff like this: 
while (<>) {
  next unless /prefix$part/;
 ...
}

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as long as the rest of the loop doesn't use any other recompile-on-demand regex. But the moment it does, you've got two regexes both being compiled on each iteration, and you get molasses at that point.

-- Randal L. Schwartz, Perl hacker
Be sure to read my standard disclaimer if this is a reply.

In reply to •Re: Re: Re: •Re: RegEx re-compilation by merlyn
in thread RegEx re-compilation by habit_forming

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