#!/usr/bin/perl

my $input = join '', <STDIN>;

unlink 'sendmail.log'
  if -f 'sendmail.log';

open my $fh, '>sendmail.log'
  or die 'Cannot write to sendmail.log';

print $fh "CLI args: @ARGV\n";
if ( defined $input && length $input ) {
  print $fh "Executed with input on STDIN\n$input";
}
else {
  print $fh "Executed with no input on STDIN\n";
}