# regex to add a comma after each char
# i believe you can think of it starting
# at the second character since
# ?<= means look to the left of the current
# position
# the . means to look at one character
# the () are required to capture each character
$show_choices =~ s/(?<=.)/,/g;
$show_choices =~ s/,$//g;       # remove the last comma

##</code><code>##

$show_choices =~ s/(.)/$1,/g;

##</code><code>##

$show_choices =~ s/(.)(?!$)/$1,/g;