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


##</code><code>##

$ perl -le " use Attribute::Constant; my $pi : Constant( 3.141592653589793 ); print $pi; $pi++"
3.14159265358979
Modification of a read-only value attempted at -e line 1.

##</code><code>##

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