gistfile1.sh

#!/usr/bin/env bash

hexify() {
  xxd -c 1 -p | sed 's/^00$/,/' | tr ',\n' '\n '
}

search="/Users/sam/.rbenv/versions/1.9.3-dev"
replace="/usr/local"

search_hex="$(echo -n "$search" | hexify)"
replace_hex="$(echo -n "$replace" | hexify)"

hexify < "$1" |
awk '
  BEGIN {
    search_hex=" '"$search_hex"'";
    replace_hex=" '"$replace_hex"'";
    split(search_hex, search);
    split(replace_hex, replace);
    search_len=length(search);
    replace_len=length(replace);
  }
  { matched=0 }
  / '"$search_hex"'/ {
    result=replace_hex substr($0, length(search_hex) + 1);
    for (i=length(replace)+1; i<=length(search); i++)
      result=result "00 ";
    print result;
    matched=1
  }
  { if (matched == 0) print $0 }
' | 
sed 's/$/00/' |
xxd -p -r