I don't see how that works. The code still runs at run-time, and the use statement still runs at compile time. Using  $x instead of  $x == 1 in the ternary eliminates a "Use of uninitialized value $x in numeric eq (==) ..." warning, but that's all. 

>perl -wMstrict -le
"my $x;
 BEGIN {
   my $m = `uname -m`;
   print qq{m '$m'} if $m =~ /x86/;
   $x = 1 if $m =~ /x86/;
   use constant FOO => ($x ? 'true' : 'false');
   }
 print FOO;
 print qq{x '$x'};
"
m 'x86
'
false
x '1'

[download]

Update: This seems to work: 

>perl -wMstrict -le
"BEGIN {
   use constant X   => (`uname -m` =~ /x86/) ? 1 : 0;
   use constant FOO => (X ? 'true' : 'false');
   }
 print FOO;
 print q{X '}, X, q{'};
"
true
X '1'

[download]

Update: Oh, wait... I didn't catch the fact that the  use constant statement is outside the BEGIN block! tobyink's code works as advertised (per tobyink's reply which I didn't see until after I had posted this update). Evidently it helps if you test the actual code. Nevermind. 

>perl -wMstrict -le
"my $x;
 BEGIN {
   my $m = `uname -m`;
   print qq{m '$m'} if $m =~ /x86/;
   $x = 1 if $m =~ /x86/;
   }
 use constant FOO => ($x ? 'true' : 'false');
 print FOO;
 print qq{x '$x'};
"
m 'x86
'
true
x '1'

[download]

In reply to Re^4: Unable to assign value to constants using ternary operator by AnomalousMonk
in thread Unable to assign value to constants using ternary operator by sathya_myl

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