Basically the first /e replaces the first s with an lcfirst version of the string (which is actually
exactly the same as the first char is a space) so we now have this in $_:

$_=" ILwHChJwulrZrjqBkNAILwHChJwulrZrjqBkNAsA1XV8FM1
pbl1PRZA8wJM8A8R1g8tm88XVNgNL11rWVPvJ1P181hNP1a881SR8QWM8
qwWAngt8ugnAK181v181KxSLdi18E18TJTMY1b8TJE8T8Z1888DB8bEj8
1WRABvGZ1Y1V8fAna111AQATJnbL81C1HzuPyJQIaIWNLqSxsLwo^ 
reverse ILwHChJwulrZrjqBkNAsA1XV8FM1pbl1PRZA8wJM8A8R1g8tm
88XVNgNL11rWVPvJ1P181hNP1a881SR8QWM8qwWAngt8ugnAK181v181K
xSLdi18E18TJTMY1b8TJE8T8Z1888DB8bEj81WRABvGZ1Y1V8fAna111A
QATJnbL81C1HzuPyJQIaIWNLqSxsLwrA1XV8FM1pbl1PRZA8wJM8A8R1g
8tm88XVNgNL11rWVPvJ1P181hNP1a881SR8QWM8qwWAngt8ugnAK181v1
81KxSLdi18E18TJTMY1b8TJE8T8Z1888DB8bEj81WRABvGZ1Y1V8fAna1
11AQATJnbL81C1HzuPyJQIaIWNLqSxsLwo^ reverse LwHChJwulrZrj
qBkNAsA1XV8FM1pbl1PRZA8wJM8A8R1g8tm88XVNgNL11rWVPvJ1P181h
NP1a881SR8QWM8qwWAngt8ugnAK181v181KxSLdi18E18TJTMY1b8TJE8
T8Z1888DB8bEj81WRABvGZ1Y1V8fAna111AQATJnbL81C1HzuPyJQIaIW
NLqSxsLwr"
[download]

(without the linebreaks)
This is actually three strings (split by ^).
These three strings are ^'d by the second /e which produces this:

ILwHChJwulrZrjqBkNA;;;;;;;;;;;;;;;;;;;;print$#{$#=
pack V6,unpack N6,join$",tsuJona,rehtreP,ah,lrekc}if$\=$/
__END__
[download]

which is the actual japh - this is evaled by the third e....
very very nice. I must admit - i'm curious who this anonymous monk is....