par=eval echo $1 | tr  ','  ' '       
for p in $par ; do                    
   sed "s/$p/g/" $2 
done

for each in $(echo $1 | tr  ','  ' ' )
do
 sed 's/'$each'/g'  $2 >temp
 mv temp $2
done
cp $2 $3

[/tmp]$ cat try.ksh
#! /bin/ksh

echo $1

par=$(echo $1 | tr  ','  ' ')
echo $par
finalPattern=""
for pattern in $par
do
    finalPattern=${finalPattern}"s/$pattern/g;"
done

sed -e "${finalPattern}" $2
[/tmp]$ cat in
p1 w1
p2 p1 w1 w3
p3 p4
p33 p2 p24 p1 p4
p4 p2
p2
p1
[/tmp]$ ./try.ksh p1/w1,p2/w2,p3/w3,p4/w4 in
p1/w1,p2/w2,p3/w3,p4/w4
p1/w1 p2/w2 p3/w3 p4/w4
w1 w1
w2 w1 w1 w3
w3 w4
w33 w2 w24 w1 w4
w4 w2
w2
w1
[/tmp]$

"s/pattern/replacement/global_flag"

#!/bin/ksh
OLD_IFS=$IFS
PAIRS=$1
IN_FILE=$2
LINES=`cat $2 | wc -l`   # LINES=$(wc -l < $2)
OUT_FILE=$3
let count=0
IFS=,
rm $OUT_FILE
touch $OUT_FILE          # The rm $OUT_FILE and touch $OUT_FILE can be replaced with :>$OUTFILE
for P in $PAIRS ; do
  if [[ count -eq 0 ]] ; then
    IN_FILE=$IN_FILE
  else
   IN_FILE=$OUT_FILE
  fi
  echo $P
  OLD=${P%/*}
  NEW=${P##*/}
  echo $OLD - $NEW
  sed "s/$OLD/$NEW/g" $IN_FILE >> $OUT_FILE
  ((count=count+1))
done
tail -n $LINES $OUT_FILE  > /tmp/tmp.file
mv /tmp/tmp.file $OUT_FILE