$ perl -MO=Concise -we 'sub parse{${$_[0]}=~/\Gfoo/gc or die} parse \(""."foo") for 1..2'
...
a   <1> srefgen sKM/1 ->b
-      <1> ex-list lKRM ->a
9         <$> const(PV "foo") sPRM/FOLD ->a
...
$ perl -MO=Concise -we 'sub parse{${$_[0]}=~/\Gfoo/gc or die} parse \("foo") for 1..2'
...
9   <$> const(IV \"foo") sM/FOLD ->a
...