4 of 13 deleted 39 characters in body

Perl 5, 56 bytes

53 bytes plus three for the flags: perl -lpF script.pl

$"='';/#+/;{unshift@F,pop@F;++$i<"$`$'"&&redo}$_="@F"

I stole the concatenate(input,input) trick from other answers here.

Explanation:

  • -lpF reads the input, removes the trailing newline, splits up the remainder into characters, and puts that split into the array @F.
  • $"='' makes sure that when we stringify an array it has no spaces in it.
  • /#+/ finds #s in the input string and sets $` equal to the stuff before it and $' equal to the stuff after it. $'$` is thus the number of times to rotate the array.
  • Now comes a loop: We increment $i (which starts at 0) and test against $'$` (the number of times to rotate); if we haven't reached $'$` yet, we redo the loop. What does the loop do? Simple: it rotates the array (pops the last element and unshifts it onto the beginning).
  • After the loop exits, we assign the stringified shifted loop to $_ so that -p prints it.