In Bash, ksh93zsh or zsh¹ksh93u+m 1.0.6 or newer¹, you can use the ${parameter/#pattern/string} pattern substitution parameter expansion operator from ksh93 to prepend -l to each array element. You may then redefine your array like this:
array=( "${array[@]/#/-l}" )
Note that if the source was sparse, a relatively uncommon case, this will reset the indexes to 0 through N-1.
¹ yash and mksh also have thatThat operator is initially from ksh93 in 1993, but in current versions, yash doesn'tinitially didn't perform any substitution if the pattern iswas empty. yash and mksh also support that operator but yash still behaves like ksh93 originally and in mksh, it cannot be performed on array expansions.