They're not 100% identical, as the following code shows: 
use warnings;
use FileHandle;

$fh = new FileHandle "file", "r";
if (defined $fh) {
  print <$fh>;
  undef $fh;       # automatically closes the file
}

$fh2 = new FileHandle "file", "r";
if (defined $fh2) {
  print <$fh2>;
  close $fh2;       # automatically closes the file
}

print <$fh>;
print <$fh2>;

[download]
Output: 
Use of uninitialized value in <HANDLE> at t line 16.
readline() on unopened filehandle at t line 16.
readline() on closed filehandle GEN1 at t line 17.

[download]

Doing a close seems to maintain some information about the filehandle, and the variable stays defined. Doing an undef unsurprisingly undefs the variable, so you get a slightly different warning, and an extra one about it being udnefined.

In reply to Re: FileHandle: undef vs close by Crackers2
in thread FileHandle: undef vs close by vinoth.ree

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