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As far as I am aware, there are only two situations in which the context of a subroutine can affect or refer in any way to the context of its caller, viz:

  1. If the caller provides a reference to a particular value, explicitly or implicitly, then the subroutine may employ the reference, as any other piece of code equally can.
  2. Perl supports closures, which consist of CODE references as in the following one-liner example:
    sub bar { my $foo="bar"; return sub { print "foo is $foo\n"; } } my $fn = bar(); &$fn; foo is bar
    Note how the function returned by sub bar references the local variable $foo and how the value remains accessible when the main-program invokes the subroutine (“closure”...) denoted by that result.

eval has two distinct meanings:   on-the-spot evaluation of the contents of a character string, and trapping of run-time errors.   In both instances, AFAIK, they are treated as lexical blocks occurring at that point.   (In the latter case, the block would be the same even if the keyword eval did not precede it.)

In reply to Re: Context propagation into subs and evals by sundialsvc4
in thread Context propagation into subs and evals by LanX

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