Re^2: why avoid & on function call

[choroba]

The placement of a sub is important onlymainly when you call it without parentheses, i.e. as a bareword. When such a call is being parsed, the subs already parsed are recognised and the bareword is parsed as their call, otherwise without strict, the bareword is stringified, and with strict, you get an error.

#!/usr/bin/perl
use warnings;

print "", frob();  # 12
print "", frob;    # frob

use strict;

print "", frob();  # 12
# print "", frob;

sub frob {
    12
}

Uncommenting the last last print line would make the source unparsable with

Bareword "frob" not allwoed while "strict subs" in use

Updated: as shown in the text, thanks kcott.

[kcott]

"The placement of a sub is important only when you call it without parentheses, ..."

I disagree with the inclusion of the word only in that statement. Here's a situation where placement is important when parentheses are used:

$ perl -wE '
    sub meaning () { 42 }
    say meaning();
'
42

$ perl -wE '
    say meaning();
    sub meaning () { 42 }
'
main::meaning() called too early to check prototype at -e line 2.
42

You can, of course, predeclare and leave the definition for later:

$ perl -wE '
    sub meaning ();
    say meaning();
    # ... later in code with other subroutine defintions
    sub meaning () { 42 }
'
42

[LanX]

Bareword use without parens is also the reason why the sub NAME; syntax without function {BODY} exists.

One can pre-declare functions for the first parse, which are later defined (or resolved via AUTOLOAD)

  DB<188> sub frob; frob(1,2,3); sub frob { say "@_" }
1 2 3

  DB<189>