#!/usr/bin/perl
#!/dfs/prod/ipn/bin/perl

$CoC_Number=123;
print "With \$CoC_Number=123,\n\n";
print "\n-----------------  print function  -----------------\n\n";

print "This is print using commas, i.e.\nprint \"Extracting CoC number \" , \$CoC_Number+1 , \" ...\\n\"\n";
  print "Extracting CoC number " , $CoC_Number+1 , " ...               which is as expected.\n";
# prints Extracting CoC number 124 ...               which is as expected.


print "\nThis is print using periods, i.e.\nprint \"Extracting CoC number \" . \$CoC_Number+1 . \" ...\\n\"\n";
  print "Extracting CoC number " . $CoC_Number+1 . " ...                                       which is NOT as expected.\n";
print "     Evidently, the dot operator (concatenation) has the same precedence as\n";
print "     the + operator.  What's happening is Perl is concatenating the\n";
print "     \"Extracting CoC number \" string with \$CoC_Number (123) and adding 1 to\n";
print "     that.  But the C language a2i routine parses \"Extracting CoC number 123\"\n";
print "     looking for an integer, stops at the first non-digit (the \"E\"), and\n";
print "     returns a 0, so the string so far is 0+1, or 1.  Then Perl concatenates\n";
print "     another string to that, resulting in the string \"1 ...\".\n";
# prints 1 ...                                       which is NOT as expected.
#   also     Evidently, the dot operator (concatenation) has the same precedence as
#   also     the + operator.  What's happening is Perl is concatenating the
#   also     "Extracting CoC number " string with $CoC_Number (123) and adding 1 to
#   also     that.  But the C language a2i routine parses "Extracting CoC number 123"
#   also     looking for an integer, stops at the first non-digit (the "E"), and
#   also     returns a 0, so the string so far is 0+1, or 1.  Then Perl concatenates
#   also     another string to that, resulting in the string "1 ...".


print "\nThis is print using periods and parenthesis, i.e.\nprint \"Extracting CoC number \" . (\$CoC_Number+1) . \" ...\\n\"\n";
  print "Extracting CoC number " . ($CoC_Number+1) . " ...               which is ok again.\n";
# prints Extracting CoC number 124 ...               which is ok again.

print "\n\n\n";

# ---------------------------  Assignment   --------------------------- #
print "\n-----------------  Assignment      -----------------\n\n";

print "This is assignment using commas, i.e.\n\$a = \"Extracting CoC number \" , \$CoC_Number+1 , \" ...\"\nthen a print \"\\\$a=>\$a<\\n\"\n";
  $a = "Extracting CoC number " , $CoC_Number+1 , " ...";
  print "\$a=>$a<                 which is just a wrong use of the comma operator,\n";
  print "                                            but it shows that assignment has a higher\n";
  print "                                            precedence than the comma operator.\n";
# prints $a=>Extracting CoC number <                 which is just a wrong use of the comma operator,
#   also                                             but it shows that assignment has a higher
#   also                                             precedence than the comma operator.


print "\nUsing parenthesis changes it, i.e.\n\$a = (\"Extracting CoC number \" , \$CoC_Number+1 , \" ...\")\nthen a print \"\\\$a=>\$a<\\n\"\n";
  $a = ("Extracting CoC number " , $CoC_Number+1 , " ...");
  print "\$a=>$a<                                   Again, just wrong use of the comma operator,\n";
  print "                                            but shows right-most value being returned.\n";
# prints $a=> ...<                                   Again, just wrong use of the comma operator,
#   also                                             but shows right-most value being returned.";


print "\nDoing assignment correctly using periods instead of commas, i.e.\n\$a = \"Extracting CoC number \" . \$CoC_Number+1 . \" ...\"\nthen a print \"\\\$a=>\$a<\\n\"\n";
  $a = "Extracting CoC number " . $CoC_Number+1 . " ...";
  print "\$a=>$a<                                  which is NOT as expected (same reason as above).\n";
# prints $a=>1 ...<                                  which is NOT as expected (same reason as above).


print "\nAgain, using parenthesis fixes things, same as above, i.e.\n\$a = \"Extracting CoC number \" . (\$CoC_Number+1) . \" ...\"\nthen a print \"\\\$a=>\$a<\\n\"\n";
  $a = "Extracting CoC number " . ($CoC_Number+1) . " ...";
  print "\$a=>$a<          which is ok.\n";
# prints $a=>Extracting CoC number 124 ...<          which is ok.