I had always used perl -d -e 1 too. It looks like there are some advantages to using re.pl if you like that sort of thing though.

@Anonymous – I’ll take a look at those. Thanks for the tip.

@garu – yes I noticed that the prompt hadn’t changed. However, clearly the re.pl has done the wrong thing. I didn’t finish the statement with a semi-colon so it should have been able to detect the continuation.

Simple example (warning! funky code ahead):

perl -Mstrict -Mwarnings -E ‘sub foo; sub foo; sub foo;’

of course, it’s valid Perl, because you’re just declaring a function, not defining it.

perl -Mstrict -Mwarnings -E ‘sub foo; sub foo; sub foo; foo(42)’
Undefined subroutine &main::foo called at -e line 1.

And now you probably now what went wrong inside the REPL as well.

The shell prefix should have given you enough of a hint, take a look at how it stays a “$” after you declare your sub:

$ sub f
$ {

and changes to a long-call “>” prefix in your latter example:

$ sub f {
> say ‘h’;

what the REPL did on the first try was declare a sub, then go inside a block – just notice how it processes and return the block right after you enter “}”, which does not happen on the second try.

Granted, a REPL specific warning about sub declaration without definition would be very helpful, specially to REPL newcomers.

Anyway, nice article!