use strict;
use warnings;

my $fn = q{abc/abc.txt};

print qq{\nTest 1:\n};
print do{
   open my $fh, $fn or die qq{open: Test 1: \n};
   <$fh>;
   };

print qq{\nTest 2:\n};
print do{
   open my $fh, qq{<$fn} or die qq{open: Test 2: \n};
   <$fh>;
   };

print qq{\nTest 3:\n};
print do{
   open my $fh, qq{< $fn} or die qq{open: Test 3: \n};
   <$fh>;
   };

print qq{\nTest 4:\n};
print do{
   open my $fh, q{<}, $fn or die qq{open: Test 4: \n};
   <$fh>;
   };

print qq{\nTest 5:\n};
print do{
   open my $fh, q{<}, \$fn or die qq{open: Test 5: \n};
   <$fh>;
   };

print qq{\n};