> perl
{ use warnings; }
print $x;
<EOF>

 > perl
BEGIN { if( {require warnings} ) { warnings->import(); } }
print $x;
<EOF>
Use of uninitialized value in print at - line 3.

 > perl
BEGIN { eval { require warnings; import warnings; } }
print $x;
<EOF>
Use of uninitialized value in print at - line 3.

 >