in reply to conditional statement in substitution expression

$line =~ s/\Q**\E(([^*]+)\Q**\E\s,\s\Q**\E([^*]+))\Q**\E(\s,)?/ "$2$3"
+ =~ tr!_!! ? "**$2_($3)**" : "**$1**" /eg;

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In Section Seekers of Perl Wisdom