Problem with Shell script

mm=`date +%b`
dd=`date +%d`
dd=`expr $dd - 1`
dt=`echo  $mm $dd

#!/usr/bin/sh
#
# Get month and days of month and year
yy=`date +%Y`
mm=`date +%m`
dd=`date +%d`
# Get yesterday
dd=`expr $dd - 1`
# Have we dropped into previous month?
if [ $dd -lt 1 ]
then
# Get previous month
  mm=`expr $mm - 1`
# Have we dropped into previous year?
  if [ $mm -lt 1 ]
  then
    mm=12
    yy=`expr $yy - 1`
  fi
# Now, feed that new month into cal to get last day number
  dd=`cal $mm $yy | tail -1 | awk '{print $(NF)}'`
fi
# If single digit, pad with a space
if [ $dd -lt 10 ]
then
  dd=" $dd"
fi
# Now use similar method to get the month name
mm=`cal $mm $yy | head -1| awk '{print $1}' | cut -c1-3`
dt="$mm $dd"

Aug.10
.Aug.9

Aug.10
Aug..9

mm=`date +%b`
dd=`date +%d`
dd=`expr $dd - 1`
dt=`printf "%s %d"  $mm $dd`

#!/bin/ksh

yesterday()
{
  perl -e '
     # today minus 86400 seconds is this time yesterday
 	 $yesterday = time - 86400;  
 	 
 	 # this line gets the month name
 	 $month = (Jan,Feb,Mar,Apr,May,Jun,Jul,Aug,Sep,Oct,Nov,Dec)[(localtime $yesterday)[4]];
 	 
 	 # day of the month
 	 $day = (localtime $yesterday)[3];
 	 print "$month $day", "\n";
  ' 
}

echo "Day before today was $( yesterday )"

mm=`date +%b`
dd=`date +%d`
dd=`expr $dd - 1`
if [ "$dd" -ge "10" ]
then 
dt=`echo "$mm $dd"` 
else 
dt=`echo "$mm  $dd"` 
fi