strict irony

[J Krugman]

use strict;

print "Ain't it ironic?\n" if strict;
print "The things you learn...\n" if BAREWORD;
print "What's going on here?\n" if bewildered;

# but if this line is uncommented, script won't compile:
# my $x = BAREWORD;

# ...will wonders ever cease?
#
# jill

 

[Matt Garrish]

use strict;

print "Ain't it ironic?\n" if strict;
print "The things you learn...\n" if BAREWORD;
print "What's going on here?\n" if bewildered;

# but if this line is uncommented, script won't compile:
# my $x = BAREWORD;

# ...will wonders ever cease?

What wonders? That you're using strictures but not warnings?

Matt

 

[Jay Tilton]

: use strict;
:
: print "Ain't it ironic?\n" if strict;
: print "The things you learn...\n" if BAREWORD;
: print "What's going on here?\n" if bewildered;
:
: # but if this line is uncommented, script won't compile:
: # my $x = BAREWORD;

The 'if' modifiers are being optimized away. Why the optimizing phase
would turn a blind eye to barewords under strict subs, I don't know.

Compounding the mystery, adding "use warnings;" causes the missing
"Bareword not allowed" compilation errors to surface. Changing 'if' to
'unless' causes compilation errors as well.

A most curious discovery.

 

[J Krugman]

What wonders? That you're using strictures but not warnings?

The code above should not compile, irrespective of whether warnings
are on or off. In fact, I just learned that it's a bug, not a
feature: http://tinyurl.com/3gfcr .

jill

 

[Jeff 'japhy' Pinyan]

: use strict;
:
: print "Ain't it ironic?\n" if strict;
: print "The things you learn...\n" if BAREWORD;
: print "What's going on here?\n" if bewildered;

The 'if' modifiers are being optimized away. Why the optimizing phase
would turn a blind eye to barewords under strict subs, I don't know.

I'd have to look at the source to see why, but I'm guessing that the "if
BAREWORD" construction *is* being optimized away.

Compounding the mystery, adding "use warnings;" causes the missing
"Bareword not allowed" compilation errors to surface. Changing 'if' to
'unless' causes compilation errors as well.

That's because 'unless' is merely 'if not ...', so there is no longer an
"if BAREWORD" construct, there is an "if not BAREWORD", which is
apparently not covered by this optimization.

This optimization is, of course, compile-time, so don't be surprised that

use strict;
print "ok\n" if FALSE;
use constant FALSE => 0;

prints "ok". The removal of the conditional happens before the 'use
constant' line is reached.

 

[Matt Garrish]

: use strict;
:
: print "Ain't it ironic?\n" if strict;
: print "The things you learn...\n" if BAREWORD;
: print "What's going on here?\n" if bewildered;
:
: # but if this line is uncommented, script won't compile:
: # my $x = BAREWORD;

The 'if' modifiers are being optimized away. Why the optimizing phase
would turn a blind eye to barewords under strict subs, I don't know.

Unless I'm missing something obvious, I don't see the issue here. Until you
attempt to assign a bareword to a variable, why would strictures complain?

Matt

 

[Jeff 'japhy' Pinyan]

Unless I'm missing something obvious, I don't see the issue here. Until you
attempt to assign a bareword to a variable, why would strictures complain?

Because 'strict "subs"' is supposed to behave this way:

"strict subs"
This disables the poetry optimization, generating a compile-time
error if you try to use a bareword identifier that's not a sub-
routine, unless it is a simple identifier (no colons) and that it
appears in curly braces or on the left hand side of the "=>" sym-
bol.

and

if (foo) { ... }

is in direct opposition to the rules stated.

 

[Joe Smith]

Appears this is related to and limited
to use of an if conditional with a print command.

No, it's not. The unexpected behavior occurs when
an 'if' is used as a statement modifier for any statement,
not just a print() statement.

It was a bug, and has been fixed by perl edit #25147.
http://www.nntp.perl.org/group/perl.perl5.porters/87664

-Joe

 

[Joe Smith]

Thanks, Joe. I was able to recreate this oddity
only when I used a print command.

I tested it with warn() in place of print(), and
by using a function that takes arguments.

use strict;
my $a="";
sub foo { $a .= "@_"; }
foo "Ain't it ironic?\n" if strict;
foo "The things you learn...\n" if BAREWORD;
foo "What's going on here?\n" if bewildered;
print "At end: $a";

I admit I did not try any other syntax, so I am
guilty of over-generalizing when I said "any statement".
-Joe