Sample to show that It's more useful to use +eval+ and +source+ if you want to decide which command to execute in your script

twice.sh

#!/bin/bash

#Execute command twice.
#Sample to show that
# It's more useful to use +eval+ and +source+
# if you want to decide which command to execute in your script

shopt -s expand_aliases # don't work even if expand_aliases is enabled.
# $@ #don't work well: don't expand the alias
eval $@
eval $@

#sample
# alias foo='echo foo'
# ./twice.sh foo # do NOT expand the alias!!
# source twice.sh foo # DO expand the alias!!
# alias twice='source twice.sh' # you can use it as a command.