"gugus"                "gugus"
 ^^ here        and       ^^ here

##</code><code>##

"gugus"                "gugus"
 ^^ "gus"       and       ^^ "s"

##</code><code>##

"gugus"                "gugus"
 ^^ "gus" yes!            ^^ "s" no!
=> match fails,
   keep looking        => match succeeds

##</code><code>##

"gugis"
 ^^ here

##</code><code>##

"gugis"
 ^^ "gis"

##</code><code>##

"gugis"
 ^^ "gis" yes!
=> match fails

##</code><code>##

 v v v v v v  (everywhere)
" s t a r t "

##</code><code>##

 "start"
 | "tart"
 | | "art"
 | | | "rt"
 | | | | "t"
 | | | | | ""
 v v v v v v
" s t a r t "

##</code><code>##

 "start"        yes => fails
 | "tart"       no  => succeeds
 | | "art"      no  => succeeds
 | | | "rt"     no  => succeeds
 | | | | "t"    no  => succeeds
 | | | | | ""   no  => succeeds
 v v v v v v
" s t a r t "

##</code><code>##

$ perl -wMstrict -MData::Dump
while ( "start" =~ /(?!start)/pg ) {
    dd ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH};
}
__END__
("s", "", "tart")
("st", "", "art")
("sta", "", "rt")
("star", "", "t")
("start", "", "")