If a perl script gets access to a string, how can the script interpret the contents of the string as perl code and execute it? My naive attempt failed:

use diagnostics;
use warnings;
use strict;

my $a_code =<<'CODE';

sub tryme
{
   my $foo = shift;
   return $foo + 2;
}

CODE

# Intent shown here does _not_ work
my $ans = eval{ $a_code; tryme( 3 ); } or die "doesn't work";
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The error might be in the way in which the code in being packaged into the string $a_code, or in how $a_code is being used, or in both.