Match parentesis subexpressions like `grep -E` (egrep) actually don't. In pure GNU Bash and no other dependency.

regrep.sh

#!/bin/bash
########################################
# Match regex grep -E
# License: GNU GPL v3+
# Author: Valerio Bozzolan
########################################

function rtfm {
	if [ ! -z "$2" ]; then
		echo "Error: $2."
		echo
	fi
	echo USAGE:
	echo "    $command REGEX [OPTIONS].."
	echo
	echo OPTIONS:
	echo "    -m --match NUM"
	echo "               NUM     show the matching group (0: everything)"
	echo "    -t --text  TEXT    show a text"
	echo
	echo EXAMPLES:
	echo echo '"pino 123paolo456 piero"' \| $command '"[0-9]+([a-z]+)([0-9]+)"' 0
	echo echo '"pino 123paolo456 piero"' \| $command '"[0-9]+([a-z]+)([0-9]+)"' 1
	echo echo '"pino 123paolo456 piero"' \| $command '"[0-9]+([a-z]+)([0-9]+)"' 2
	echo echo '"pino 123paolo456 piero"' \| $command '"[0-9]+([a-z]+)([0-9]+)"' --text salt 0 --text pepper
	echo echo '"pino 123paolo456 piero"' \| $command '"[0-9]+([a-z]+)([0-9]+)"' --text salt 1 --text pepper
	echo echo '"pino 123paolo456 piero"' \| $command '"[0-9]+([a-z]+)([0-9]+)"' --text salt 2 --text pepper
	exit 2
}

command="$0"
regex="$1"
argc=$#
argv=($@)

if [ -z "$regex" ]; then
	rtfm "Missing regex"
fi

while IFS= read -r ln; do
	if [[ ! "$ln" =~ $regex ]]; then
		continue
	fi

	glued=
	for (( i=2, j=3; i<=argc; i++, j=i+1 )); do
	    arg1="${!i}"
		arg2="${!j}"

		case "$arg1" in
			'--text'|'-t')
				if [ -z "$arg2" ]; then
					rtfm "Missing text after $arg1"
				fi

				glued="$glued$arg2"
				(( i++ ))
			;;
			'--match'|'-m')
				if [ -z "$arg2" ]; then
					rtfm "Missing number after $arg1"
				fi

				glued="$glued${BASH_REMATCH[$arg2]}"
				(( i++ ))
				;;

			*)
				glued="$glued${BASH_REMATCH[$arg1]}"
				;;
		esac
	done

	if [ "$glued" ]; then
		echo "$glued"
	else
		echo "$ln"
	fi
done < /dev/stdin