Patch __fasd_run.fish to use fish built-in functions

This is based from this PR: fishgretel/fasd#23

private_dot_config/fish/conf.d/__fasd_run.fish

@@ -1,19 +1,19 @@
 function __fasd_expand_vars -d "Expands only the first occurance of a variable in the passed string without evaluating the string"
-  set -lx vars (echo -n $argv | grep -oP '(?!\\\\)\$\K([A-z_][A-z0-9_]*?)([^A-z0-9_]|\b|\n)' | perl -pe 's/(.+?)(?:[^A-z0-9_]|\b)$/\1\n/' | sort -u)
+  set -lx vars (string match -a -r '(?!\\\\)\$\K([A-z_][A-z0-9_]*?)(?:[^A-z0-9_]|\b|\n)' "$argv" | string replace -r '(.+?)(?:[^A-z0-9_]|\b)$' '$1' | sort -u)
   for var in $vars
     # Only replace if the variable is defined
     if set -q $var
       # Replacing the variable once is enough
-      set argv (string replace -r '([^\\\\]|\b)\$'"$var" '$1'"$$var" "$argv") 
+      set argv (string replace -r '([^\\\\]|\b)\$'"$var" '${1}'"$$var" "$argv")
     end
   end
   # The following pipe does the same thing as fasd --sanitize
-  printf '%s\\n' "$argv" | sed -e 's/\([^\]\)$( *[^ ]* *\([^)]*\)))*/\1\2/g' -e 's/\([^\]\)[|&;<>$`{}]\{1,\}/\1 /g' | tr -s " " \n
+  printf %s\n $argv | sed -e 's/\([^\]\)$( *[^ ]* *\([^)]*\)))*/\1\2/g' -e 's/\([^\]\)[|&;<>$`{}]\{1,\}/\1 /g' | tr -s " " \n
 end
 
 function __fasd_run -e fish_postexec -d "fasd records the directories changed into"
-  set -lx RETVAL $status
-  if test $RETVAL -eq 0 # if there was no error
+  if test $status -eq 0  # if there was no error
     command fasd --proc (__fasd_expand_vars $argv) > "/dev/null" 2>&1 &
+    disown
   end
 end