Question

I’m teaching myself Perl with the help of some internet tutorials, and for the most part it’s going really well and everything runs smoothly. However, I cannot do ANY comments, whatsoever, or the program won’t run properly. For example, the following code:

#eee
print "Estimation of Pi";

will run, but not print anything, while just this

print "Estimation of Pi";

runs and prints what it’s meant to.

What am I doing wrong? I don’t understand this at all.

Also, on a side note, what is #!/usr/bin/perl needed for? My programs seem to be running fine without it (and being a comment, the programs don’t work WITH it)

Answer 1

I suspect your file doesn’t contain what you think it does. Perhaps you have a CR instead of a LF or CRLF.

>perl -e"binmode STDOUT; print qq{#eee\rprint qq{foo\\n}}" | perl

>perl -e"binmode STDOUT; print qq{#eee\nprint qq{foo\\n}}" | perl
foo

>perl -e"binmode STDOUT; print qq{#eee\r\nprint qq{foo\\n}}" | perl
foo

Examine your file with a hex editor, or at worse with the following command:

perl -0777nE"BEGIN { binmode STDIN } say join ' ', unpack '(A2)*', unpack 'H*', $_" < file

#! is a unix concept. Windows doesn’t use it, but Perl will look for command line option on that line. For example, the following will warn:

#!perl -w
print undef;