I was recently wondering how to do this, and why a regular anonymous sub (w/o closures) wouldn't work. Then I found this node. Though my solution (before finding this) was to generate an anonymous sub using eval $string. E.g.

my $range_checker = eval 'sub { local $_ = shift; /foo/../bar/ }';
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At first, your way seems a little too indirect and magical, but it makes perfect sense if you create a 'flip-flop generator':

sub mk_flip_flop {
  my ( $re1, $re2 ) = @_;
  sub { local $_ = shift; /$re1/../$re2/ }
}
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