unset f ; f=abcd

first_char=${f[@]:0:1}
recho $first_char

first_char=${f[0]:0:1}
recho $first_char

first_char=${f:0:1}
recho $first_char

first_char="${f[@]:0:1}"
recho $first_char

first_char="${f[@]:0:1}"
recho $first_char

first_char="${f[0]:0:1}"
recho $first_char

first_char="${f:0:1}"
recho $first_char

unset f;
f=( one two three )
first_word=${f[@]:0:1}
recho $first_word

first_word=${f[0]:0:1}
recho $first_word

first_word=${f:0:1}
recho $first_word

unset f;
f=( one two three )
first_word=${f[@]:0:1}
recho $first_word

set -- abc def ghi

printf '<%s> ' "123 $@ 456"; echo
printf '<%s> ' "123 $@\ 456"; echo