sub m1{1+4*y/VLD//.E.ord()x3%75%50%4}
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sub m3{5**y/VLD//.E.ord()x3%75%50%4}
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This is much longer than yours, but I thought I'd still mention it:

sub b0{(1e3,10,5,1,100,500,50)[ord()%87%7]}
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Update: a new one that's only one character too long

sub b1{M1E3D500C100L50X10V5I1=~$_;$'}
[download]