pathmunge() bash function to add to PATH without duplication

pathmunge.sh

pathmunge () {
	if [ "$2" = "force" ] || ! echo $PATH | $(which egrep) -q "(^|:)$1($|:)"
	then
		if [ "$2" = "after" ]
		then
			PATH=$PATH:$1
		else
			PATH=$1:$PATH
		fi
		export PATH
	fi
}

Usage: pathmunge <new_path> [after|force]

Adds new_path to the beginning of PATH unless it already exists.

Options:
    after : Add new_path to the end of PATH
    force : Add new_path regardless of duplicates

There's no quote for the PATH assignments, then if there's space or something alike in "$1" or "$PATH", then the function behaviour is undefined.

And also, why bother using which and egrep, they are external commands and just too slow.