bash script - find files matching filename pattern, search first line for matching pattern

gistfile1.txt

#!/bin/bash
for f in `find -E . -regex ".*ext1|.*ext2|.*ext3"`
do
  line=$(head -n 1 $f)
  if [[ $line =~ TextAtStartOfLine:[[:space:]]*([[:digit:]]+) ]]; then
    echo "${BASH_REMATCH[0]}" # print whole match
    echo "${BASH_REMATCH[1]}" # print 1st group match
  fi
done