$ perl -del
DB<1> x 0+( () = join('','','x'x(1<<30),'') =~ m{}g )
0 1
DB<2> x 0+( () = join('','','x'x(1<<31),'') =~ m{}g )
0 0
DB<3> x 0+( () = join('','','x'x((1<<31)-8),'') =~ m{}g )
0 1
DB<4> x 0+( () = join('','','x'x((1<<31)-7),'') =~ m{}g )
0 0
####
$ perl -del
DB<2> x 0+( () = join('',('','x'x((1<<30)-10),'')x2) =~ m{}g )
0 2
DB<1> x 0+( () = join('',('','x'x((1<<30)-10),'')x3) =~ m{}g )
0 0
##
##
$ perl -del
DB<1> $x = join('',('','x'x((1<<30)-10),'')x2); while( $x =~ m{}g ) { print pos($x), $/ }
1073741821
2147483642
DB<1> $x = join('',('','x'x((1<<30)-10),'')x3); while( $x =~ m{}g ) { print pos($x), $/ }
DB<2>