In contrast, consider matching and deleting only that which you wish to eliminate from the string:

>perl -wMstrict -le
"my $line = 'B6y green $1$Byf3501d$dPtaW2vCbq63sdsw';
 $line =~ s{ \s \S+ $ }{}xms;
 print qq{'$line'};
"
'B6y green'
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