The question is a little vague but I will gove some examples and hope this helps:

#have a cgi var default to something

#option 1
$x = $cgi->param("input_var") or "foo";
#option 2
$x = $cgi->param("input_var") || "foo";

#have open a file or die 

#option 1
open( HANDLE, "foo.txt" ) or die;
#option 2
open( HANDLE, "foo.txt" ) || die;

#have some sort of logic test
#option 1
if( $x eq "foo" or $y eq "bar" )
#option 2
if( $x eq "foo" || $y eq "bar" )
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