$ hexdump -C foo
00000000  61 0a 30                                          |a.0|
00000003
$ perl -wle 'print "read line" while (my $x  = <>)' foo
read line
read line
$

##</code><code>##

$ perl -MDevel::Peek -wle 'while (my $x  = <>){ print "read line"; print "and its true" if $x }' foo
read line
and its true
read line