ksh: Comparing strings that contain spaces and working with substrings

Forgive me. I am very new to kornshell scripts. The simplest things stop me dead in my tracks.

Here are two such examples.

I want to save the first 19 characters of the following string to a variable.

"Operation Completed and blah blah blah"

I know this works (from another thread):

mystring="Operation Completed and blah blah blah"
echo $mystring | cut -c 1-19

But I cannot figure out how to save the output of the result of the cut command to a variable.

So because I could not do that, I tried to compare the result of the cut command to a variable containing "Operation Completed", only I can't get the comparison to work. I keep getting :Operation not found when I run the following shell.

cstring="Operation Completed"
mystring="Operation Completed and blah blah blah"
echo $mystring | cut -c 1-19
if [[ "$cstring" = $($mystring | cut -c 1-19) ]]; then
echo "they match"
fi

Thanks in advance.

some ways:

mystring="Operation Completed and blah blah blah"
echo $mystring | cut -c 1-19 | read myvariable
# or --------
myvariable=$(echo $mystring | cut -c 1-19 )
# or ---
myvariable=`echo $mystring | cut -c 1-19`

The ` bactick syntax is old but is allowed.

if [ "$cstring" = "$(echo $mystring | cut -c 1-19)" ]; then
  echo "they match"
fi