Input: 2d4+10
Code: s/d/q(+~~rand($')+d)x$`/e;

2d4+10
2(q(+~~rand($')+d)x$`)4+10
2(q(+int(rand($'))+d)x$`)4+10
2(q(+int(rand(4+10))+d)x2)4+10
2('+int(rand(4+10))+d'x2)4+10
2('+int(rand(4+10))+d''+int(rand(4+10))+d')4+10
=?????
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2d4+10

2(q(+~~rand($')+d)x$`)4+10

2(q(+int(rand($'))+d)x$`)4+10

2(q(+int(rand('4+10'))+d)x2)4+10

2('+int(rand('4+10'))+d'x2)4+10

2('+int(rand('4+10'))+d'.'+int(rand('4+10'))+d')4+10

2+int(rand(4))+d+int(rand(4))+d4+10

# or looking at each term

2             # since rand return 0..N-1 instead on 1..N, we add one f
+or every die

+int(rand(4)) # int in 0..3

+d            # 0

+int(rand(4)) # int in 0..3

+d4           # also 0, the 'd' are here to help ignore the 4

+10           # desired extra

# then eval that :)
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Awesome, thank you! With a little bit of experimenting now, I found that rand(4+10) would pick 0...13, but rand('4+10') picks 0...3, ignoring everything beyond the first string of digits. I didn't realize that odd behavior, nor did I realize you could make something like 'd4', which is ignored when evaluating the statement, instead of causing an error. Those seem like odd loopholes in the way Perl works, but that just makes the whole command that much more beautiful. Thanks again!