# loop through every file named on the command line, setting
# $_ to each successive line
while (<>) {
  chomp;  # remove any line ending (implicitly uses $_)

  # ... aha! the interesting part goes here
  my @fields = split /\|/;  # implicitly uses $_

  # Now we have the values for this row in $fields[0], $fields[1], ...

  # write to STDOUT
  print join( ',', @fields ), "\n";
}