There's a built in pragma called constant which I'd probably reach for before trying to do something clever with typeglobs:

$ perl -Mstrict -Mwarnings -le '
    use constant MYVAR => 3.14159;
    print MYVAR;
    use constant PI => 4 * atan2(1, 1);
    print PI;
'
3.14159
3.14159265358979
[download]

However, if you're stuck with the typeglob, I'd take a pragmatic approach and pick the one which involves the least typing (i.e. ${*myVar}).

$ perl -Mstrict -Mwarnings -le '
    *myVar = \3.14159;
    print ${*myVar};
    print ${*myVar{SCALAR}};
    print $main::myVar;
'
3.14159
3.14159
3.14159
[download]

If you don't want to declare with our or use constant (maybe also take a look at Readonly, but that seems to exact a speed penalty (Update: see thread Module Readonly, esp. the most recent reply)),  $::myVar is a little bit less typing than  $main::myVar (well, at least as long as you're in the  main package).

>perl -wMstrict -le
"*myVar = \3.14159;
 print $::myVar;
"
3.14159
[download]

G'day AnomalousMonk,

My preference would be for Const::Fast. My reasons for this are in "Re: Use of Constants". I am not, however, on a crusade to promote one over the other. :-)

-- Ken

My preference would be for Const::Fast. My reasons for this are in "Re: Use of Constants"

One caveat -- beside the build problem -- of that module that it fails to mention, is that its "constants" aren't (compile-time) constants, but rather runtime variables that cannot be varied [sic], and thus they do not trigger Perl's compile-time optimisations.

For me, that issue alone negate the purpose of using constants almost completely. Combined with the other two issues render it a non starter.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

Attribute::Constant / Data::Lock don't suffer from the restricted hashes caveat, they are still read-only variables

*var = \3.14159;
our $var;
print $var;
[download]

Technically in perl-speak, that is the typeglob way to create a read-only variable, not a constant

This is a constant  sub var() { 42 } print var;

This is a read-only

$ perl -Mstrict -le " our $var; *var= \3.14159; print $var; $var++ "
3.14159
Modification of a read-only value attempted at -e line 1.
[download]

This is fast read-only

$ perl -le " use Attribute::Constant; my $pi : Constant( 3.14159265358
+9793 ); print $pi; $pi++"
3.14159265358979
Modification of a read-only value attempted at -e line 1.
[download]

OTOH

$ perl -Mbignum=PI -le " print PI() "
3.141592653589793238462643383279502884197
[download]