# This program demonstrates prompting the user for input, searching,
# and file manipulation.  It prompts the user for an input filename, 
# an output filename, a search filename and a replacement string, and 
# replaces all occurences of the search pattern with the replacement
# string while copying the input file to the output file.
#
#Learning Perl Appendix A, Exercise 10.2
print "Input file name: ";
chomp($infilename = <STDIN>);
print "Output file name: ";
chomp($outfilename = <STDIN>);
print "Search string: ";
chomp($search = <STDIN>);
print "Replacement string: ";
chomp($replace = <STDIN>);
open(IN,$infilename) ||
    die "cannot open $infilename for reading: $!";
## optional test for overwrite...
die "will not overwrite $outfilename" if -e $outfilename;
open(OUT,">$outfilename") ||
    die "cannot create $outfilename: $!";
while (<IN>) {    # read a line from file IN into $_
    s/$search/$replace/g; # change the lines
    print OUT $_; # print that line to file OUT
}
close(IN);
close(OUT);