#!/bin/bash
match="string_I_want_to_match"
read -r -d '' str_i_want_above <<- 'EOF'
I
Want
This
Above the match
EOF
sed "/$match/i \\
${str_i_want_above//$'\n'/\\$'\n'}
" <<< "$match"
IyEvYmluL2Jhc2gKCm1hdGNoPSJzdHJpbmdfSV93YW50X3RvX21hdGNoIgoKcmVhZCAtciAtZCAnJyBzdHJfaV93YW50X2Fib3ZlIDw8LSAnRU9GJwpJCldhbnQKVGhpcwpBYm92ZSB0aGUgbWF0Y2gKRU9GCgpzZWQgIi8kbWF0Y2gvaSBcXAoke3N0cl9pX3dhbnRfYWJvdmUvLyQnXG4nL1xcJCdcbid9CiIgPDw8ICIkbWF0Y2gi