[perl #127822] [BUG] Doing two S/// with an `andthen` between them messes up $_ in Rakudo

[Carl Mäsak]

# New Ticket Created by  "Carl Mäsak" 
# Please include the string:  [perl #127822]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=127822 >


<TimToady> m: say (S/Once/Twice/ given "Once upon a time")
<camelia> rakudo-moar a87fb4: OUTPUT«Twice upon a time␤»
<TimToady> m: say (S/Once/Twice/ andthen S/a/two/ given "Once upon a time")
<camelia> rakudo-moar a87fb4: OUTPUT«atwo␤»

(Expected value here: "Twice upon two time".)

<TimToady> a rather peculiar bug
* masak submits rakudobug
<masak> m: $_ = "Once upon a time"; say (S/Once/Twice/ andthen S/a/two/)
<camelia> rakudo-moar a87fb4: OUTPUT«atwo␤»

(Expected value here: "Twice upon two time".)

<masak> m: $_ = "Once upon a time"; say ($_ ~= ", kthx" andthen S/a/two/)
<camelia> rakudo-moar a87fb4: OUTPUT«Once upon two time, kthx␤»

(This one is fine.)

<masak> ok, so both S/// are needed to trigger the bug
<masak> but not the given