Automator script getting syntax error on line 31

The above script was written to be executed (and tested) from the command line, not Automator. The following Automator solution uses one Ask for Finder Items action so one can choose the source folder and destination folder in one action using the command key.

It then prompts for the n-th value of modulo files to copy between folders and then presents these three values in the order necessary for successful Run Shell Script execution. The following was tested on Monterey 12.6.3.

Code for the Run Shell Script contents:

#!/bin/zsh

: <<"COMMENT"
Copy nth file from the SRCDIR with modulo value to the DSTDIR.
Argument 1: Source Directory
Argument 2: Destination Directory
Argument 3: n-th file number for modulo
COMMENT

# not visible in Automator
function usage () {
    printf '%s %s\n' "${ZSH_ARGZERO}" "sourcefolder destfolder nth_value"
    printf '%s %s\n' "${ZSH_ARGZERO}" "~/Desktop/TestZ ~/Desktop/BAR 3"
    return
}

# script must have three arguments or bust
((${#} == 3)) || ( usage;exit 1 )

# nth file value is third argument
typeset -gi mod=$3
typeset -ga ary=()

# force relative path references to absolute paths
SRCDIR="${1:a:s/\~\//}"
DSTDIR="${2:a:s/\~\//}"

# file extension pattern to match
FILE_EXT="*.txt"

# put plain text files into an array sorted by version
ary=( $(print "${SRCDIR}"/${~FILE_EXT}(.N) | sort -V) )
# print -l $ary

# the range is 1 to the count of files in the array
for n in {1..${#ary[@]}};
do
    # if modulo is met, then copy file and if not get next array index
    (( $n % $mod == 0 )) || continue
    # printf '%s -> %s\n' "${ary[$n]}" "${DSTDIR}/${${ary[$n]}:a:t}"
    cp -a "${ary[$n]}" "${DSTDIR}/${${ary[$n]}:a:t}"
done
unset ary mod
exit 0

Sometimes, one gets to look at previous posted code and realize that its functionality is also wrong. The original script was not selecting the matching modulo files in the array and was more complicated then it needed to be. I have fixed some of the code for accuracy and performance. The following was tested on Ventura 13.2.1.

#!/bin/zsh

: <<"COMMENT"
Copy nth file from the SRCDIR with modulo and copy them to the DSTDIR.
COMMENT

typeset -gi mod=$3
typeset -ga ary=()

# not visible in Automator
function usage () {
    printf '%s %s\n' "${ZSH_ARGZERO}" "sourcefolder destfolder nth_value"
    printf '%s %s\n' "${ZSH_ARGZERO}" "~/Desktop/TestZ ~/Desktop/BAR 3"
    return
}

# script must have three arguments or bust
((${#} == 3)) || ( usage;exit 1 )

# file extension to match
FILE_EXT="*.txt"

# force relative path references to absolute paths
SRCDIR="${1:a:s/\~\//}"
DSTDIR="${2:a:s/\~\//}"

# put plain text files into an array sorted by version
ary=( $(ls -1 "${SRCDIR}"/${~FILE_EXT}(.N) | sort -V) )
# print -l $ary

# the range is 1 to the count of files in the array
for n in {1..${#ary[@]}};
do
    # if modulo is met, then copy file and if not get next array index
    (( $n % $mod == 0 )) || continue
    # printf '%s -> %s\n' "${ary[$n]}" "${DSTDIR}/${${ary[$n]}:a:t}"
    cp -a "${ary[$n]}" "${DSTDIR}/${${ary[$n]}:a:t}"
done
unset ary mod
exit 0