It would appear to be an end of line thing. When your perl is in its own file, a comment extends to the end of the line. You can quite happyily put a semi-colon in a comment and perl just treats it as a comment.

Now extend this to the command line...

This works as expected:

perl -e 'printf "hello\n"'

This too works, as the comment is at the end:

perl -e 'printf "hello\n"; ## Comment'

This will not print anything because although the statements are separated by a semi-colon, perl has no newline to tell it where the comment ends:

perl -e '## Comment; printf "hello\n"'

This is how I entered a comment on the command line and got it to work as expected:

perl -e '## Comment; [RETURN WAS PRESSED HERE]
printf "Hello\n"'
[download]

== fx, Infinity Is Colourless

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.