print "file1 ="; 
$file1=<stdin>;
print "file2 =" ;
$file2=<stdin>;
@ARGV = ("$file1", "$file2") ;
chomp($remove = <stdin>);
chomp($replace = <stdin>);
while(defined($line=<>)){
 $line =~ s/$remove/$replace/g;
 print "$line"; }