just wondering why print() function cannot display them.
I personally believe that you're confused: as others duly explained to you, print indeed does print() them. The fact that they're control charachters makes them not visible on a plain terminal, though. The fact that some specialized tools like more or less will display them in such a way that makes them visible is totally irrelevant. Thus, to literally answer your question: "because print() is made to print stuff as opposed to especially display it." Of course, nobody prevents you from rolling your own display() sub to do so. E.g.:
sub display {
map {
(my $s = $) =~ s/[[:cntrl:]]/^A/g;
$s;
} @_;
}
Here, I just made it show any control carachter like "^A" which may be or not what you want, but I don't know of any standard mapping or representation for them. If you have one, then again feel free to just refine the thing. All that perldoc perlre has to say is: 'all characters with ord() less than 32 are usually classified as control characters (assuming ASCII, the ISO Latin character sets, and Unicode), as is the character with the ord() value of 127 ("DEL")'
To be completely fair, Perl IO routines do some translations, and if you're really motivated to have print() do it for you, then you may move your display() code to a suitable layer once you're fine with it.
