DB<116> $a="a a"
 => "a a"

  DB<117> scalar ($a =~ /a/g)
 => 1

  DB<118> scalar ($a =~ /a/g)
 => 1

  DB<119> scalar ($a =~ /a/g)
 => ""                         # exhausted

  DB<120> $a="a a"
 => "a a"

  DB<121> scalar ($a =~ /a/)
 => 1

  DB<122> scalar ($a =~ /a/)
 => 1

  DB<123> scalar ($a =~ /a/)
 => 1                          # ... till infinity